"You cannot take care of yourself, let alone the three of us"
I just wanted to know whether the phrase let alone is used correctly or not in the above sentence. Please give your opinions. Thanks in advance.
Yes, it is a correct use of the let alone construction, which is discussed in this famous paper:
Fillmore, Kay, and O'Connor, "Regularity and Idiomaticity in Grammatical Constructions:
The Case of Let Alone" , Language, Vol 64, No 3 (Sept 1988), pp 501-538.