Too X, X enough, enough X

Can someone explain why the choices not marked as 'correct' in these fill-in-the-blank questions are wrong?

It was ___ so we didn't get it.
expensive enough
too expensive -correct
enough expensive

It's _____ to read; I don't understand it at all.
enough difficult
too difficult -correct
difficult enough

It's not _____ to sort things out.
enough late
late enough
too late -correct

It's _____ to pass.
enough difficult
too difficult -correct
difficult enough

It's _____ walk—I'll take the bus.
enough far
far enough
too far -correct
too much far

Are 'much enough' ever used together? For example,

He ate _____ and felt ill.
enough much
much enough
too much

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"It's difficult enough to pass." could be fine, depending on context (and I have no idea what context would be implied in an ESL exercise). "It's difficult enough to pass. I'm not even going to try it with a boat trailer on my car." — although I believe British English uses overtake rather than pass. –  Peter Shor Sep 15 '12 at 14:03
Closed as too localized? That's the worst site for English help indeed. –  Monica Sep 15 '12 at 14:31
Very briefly, since we're closed: Too [Adj] to [Verb] is equivalent to "So [Adj] that one cannot [Verb]". [Adj] enough to [Verb] is equivalent to "So [Adj] that one can [Verb]". Enough is used before nouns, after adjectives. And enough is never used with much; in the prohibitive construction one says "too much to" and in the permissive construction simply "enough to". –  StoneyB Sep 15 '12 at 14:47
@Monica, you haven't done your research if you think ELU is “the worst site for English help indeed”. I think urbandictionary and Unpedia are far worse. –  jwpat7 Sep 15 '12 at 19:34
Voting to re-open. A good answer to this question would provide good general rules for using "too" and "enough" - common words that learners of English often use incorrectly. There is just NO WAY this question can be considered too localised. –  user16269 Sep 15 '12 at 21:46

The key point here is that if something is "too expensive", "too difficult", "too late" or whatever, then this prevents you from doing what you otherwise would.

• The car was too expensive, so I didn't buy it.
• The problem was too difficult, so I couldn't solve it.
• The party started too late, so I didn't attend.

In a sense, "enough" works the opposite way. That is, if something is "cheap enough", "easy enough", "early enough", then this enables you to do something.

• The car was cheap enough, so I bought it.
• The question was easy enough, so I posted an answer.
• The party started early enough, so I went along and stayed for a while.

Note also that when "enough" is an adverb, it follows the adjective or verb that it qualifies. When it is used as an adjective, it usually precedes the noun.

• The car had enough petrol in the tank.
• The question had enough merit to warrant being re-opened.
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I'm glad this question got reopened; this is an excellent answer. (I'll leave mine there, but, if no one else answers, I think Monica should choose yours.) –  J.R. Sep 16 '12 at 1:50
Thank you very much, David :). –  Monica Sep 16 '12 at 9:07
I am very grateful to those who voted for my question to be reopened. –  Monica Sep 16 '12 at 9:24
So 'enough' either enables you to do something or prevents you from doing something(as in this example; We didn't go out to dinner after the show; the tickets to the play were expensive enough.), but I don't see how 'far enough' means that 'it is not too far, I can walk'. –  Monica Sep 16 '12 at 9:50
@Monica: "It is not too far, I can walk" would be conveyed with close enough, not far enough, as in, "The theater is close enough, we can walk." –  J.R. Sep 16 '12 at 17:39

For many of these questions, the idea is that the word enough is not used in the same way as too or very are used; you simply don't say enough difficult, or enough expensive. When modifying an adjective, the word is enough is used after the word it modifies, not before:

He's old enough to stay out past midnight.
He's skilled enough to ski down the expert trail.

If you want to use a word before the adjective, you can use sufficiently:

He's sufficiently skilled to ski down the expert trail.

or, you can restructure the sentence, and use enough to modify a noun:

He has enough skill to ski down the expert trail.

As for this example problem:

It was ______ so we didn't get it.
a. expensive enough
b. too expensive - correct
c. enough expensive

As I mentioned previously, I can't think of an instance when I would ever say "enough expensive." As for "expensive enough", there are times I might use that wording, but not within the "It was ___, so..." construct. However, I might say:

We didn't go out to dinner after the show; the tickets to the play were expensive enough.

As for this one:

It's _____ to read; I don't understand it at all.
a. enough difficult
b. too difficult - correct
c. difficult enough

Again, (a) is just downright awkward. The third option almost works, but too difficult matches better with the speaker not understanding the reading material. If, however, the sentence had said,

It's _____ to read; I think it'll take me forever to finish that book!

then (c) might be more acceptable, because the word enough can be used for emphasis, where "difficult enough" can mean, essentially, "very difficult."

As for this one:

It's not _____ to sort things out.
a. late enough
b. too late - correct

There's nothing wrong with saying late enough, but not in this context (because it's hard to think of a context where it's too early to sort things out). Instead, one might say:

It's not late enough in the day yet to start selling our bread for half price.

(Admittedly, I'd probably opt for "too early," instead of "not late enough," but, nevertheless, that sentence is grammatical.)

I hope these explanations help you out. It's hard to tackle all six of these at once – which is why some may have voted to close the question initially. Hopefully, though, I've explained enough, so that you can figure out the ones I didn't address.

One last thought, about your comment (that this must be "the worst site for English help"): to that, I say, "Enough, already." I think there are enough helpful people on EL&U that such comments are unwarranted and unnecessary.

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+1, I might add that in the"expensive enough/too expensive" question, it is the use of so that breaks expensive enough- changing so to that would result in, "It was expensive enough that we didn't get it" which reads okay in my book. –  Jim Sep 16 '12 at 0:23