Atleast problem

[RIJU]

80 students were asked to read 3 kinds of book. 53 of them have read at least 1 kinds of book. How many students have read exact 1 book?
1) xxx people have read at least 2 kinds of the books.
2) xxx people have read 3 kinds of the books

[lego2401]

So lets put it this way,
We have people who read nothing. We have people who read one or more, two or more, or three or more. The people who read exactly one are the Total - Read Atleast 2 - read none.
1- if xxx is given to us as a number in the statements, the we know that of the 53 who read atleast 1, xxx read atleast 2, so
53-xxx = the number of people who read exactly 1. Sufficient.
2- Not needed, since atleast 2 cover this number.

answer A.