Question

If $A\times B=\{(a,1),(b,3),(a,3),(b,1),(a,2),(b,2)\}$.Find $A$ and $B$

Answer 1

Clearly,$A$ is the set of all first entries in ordered pairs in $A\times B$ and $B$ is the set of all second entries in ordered pairs in $A\times B$

$\therefore A=\{a,b\}$ and $B=\{1,2,3\}$