Question

Given A = {3, 4, 5, 6} and B = {8, 9}. State, giving reason, whether { (3, 8), (4, 9), (5, 8) } is a mapping from A to B or not. Type 1 if it is a mapping and 0 if it is not

Answer 1

A set of ordered pairs is a mapping from one set to other set when each element of the first set is uniquely associated to an element in the other set.
The given set of ordered pairs is not a mapping as element $6$ in $A$ is not associated with an element in $B$.