Question

If A = {5,6,7} and B = {2,3}, {(2,6),(2,5),(3,7)} ⊆ B×A.

Answer 1

Consider the Cartesian product $B\times A=\{(2,5),(2,6),(2,7),(3,5),(3,6),(3,7)\}$. As we can see, the pairs $(2,6), (2,5)$ and $(3,7)$ belong to the set $B\times A$. Thus, $\{(2,6), (2,5),(3,7)\}\sube B\times A$.