As this is an English Language site, the first thing to deal with is the appropriate terminology for the data you wish to present. What happened, exactly? I assume that you sent out your questionnaire to 150 people (you certainly did not send out responses), but what you received were a number (less than 150) of responses. So you cannot talk about receiving ‘x/150 responses’, or ‘x out of 150 responses’.
Avoiding for the moment the x/150 format (and not writing the numbers out), I see your choice between making the distinction explicit, e.g.
We received 134 responses out of 150 questionnaires sent out
Or, using the widely used term, response rate, which the Cambridge Dictionary defines as “the number of people who answer questions in a survey (= set of questions about a product or service) as a percentage of the number of people who are asked to take it:”
I think that this is preferable as it makes your text more compact:
The response rate was 134 out of 150
And response rate is also suitable as a table heading.
Numerals or Text
I agree with @JamesRandom that numerals should be used rather than text, but the style of the Associated Press Stylebook is generally followed in scientific journals, rather than that the Chicago Manual of Style.
Thus, on p. 16 of the issue of the highly-respected (British) journal, Nature, for 4th April 2019 we have:
“Three massive detectors…officially resumed collecting data on 1 April, after a 19-month shutdown for upgrades.”
And on p.309 in the equally-respected (US) journal, Science, for 26th April 2019 we have:
“For example, polio…has been eliminated from all but three countries, with just 33 cases last year.”
Style of expression of Response Rate
This is largely subjective.
“134/150” seems to me best suited to a table, and jars a little in text because the reader has to switch registers, as it were.
“134 out of 150” seems to me better for text, but too long for a table, where it distracts from the numbers.
“89%” or “89% (150 questionnaires sent out) ” seems to best of all because the reader isn’t required to do the arithmetic himself.
Comment on your Figure
If I were talking to a student I would be brutally honest and say that the figure is really bad. I would then explain why. Why? Because the key data — the numbers — are obscured by the repetition of much less important information, some of it emboldened even though it is in parentheses. And what information are the icons intended to convey? They just distract. I would use a table with column headings to avoid repetition, and just use #1 etc. to designate the six batches (or whatever).
An alternative style to put more emphasis on the actual rate is shown on the right.