Question

A= {1,2,3} a relation R on A is defined as R={(a,1) (2,1) (2,b)} find a and b.

Answer 1

If R is a relation on A then the set R must be
R={(1,1),(1,2),(1,3),(2,1),(2,2),(2,3),(3,1),(3,2),(3,3)}

Comparing the above set with R={(a,1),(2,1),(2,b)}
a can be 1 or 3 because (2,1) is already given.
And b can be any of 1, 2 and 3.

Hope it helps.....