U = 1,2,3,4,5,6,7,8,9

A = 1,3,5,7

B = 4,5,6

a ⊂ b True or false

and

B ⊂ U True or false

My answers are false for the first one and true for the second one

correct both times.

In general, for a given set of problems, U is the Universe. Any subsets being discussed will always be subsets of U, or things are poorly set up.