Question

Let U = {1, 2, 3, 4, 5, 6, 7}, A = {1, 2, 3, 4}, B = {1, 2, 5, 6}, and C = {3, 5, 7}. List all the members of the given set. (Enter your answers as a comma-separated list.)

Answer 1

I suspect you have missed out part of the question, such as:
a) A∪B
b) A∩B
...
etc.

Which is/are the "given set"?

Answer 2

A) {1,2,3,4,5,6}
B) {2}