An example is when A contains even numbers and B contains multiples of $4.$ We define the function $"$f$($w$)"$ as doubling the number represented by input string $"$w$."$ If $"$w$"$ is even $($in A$),$ then $"$f$($w$)"$ is a multiple of $4($in B$).$ This function acts as a bridge between A and B$,$ making it easier to determine whether a string belongs to A by checking its translated version in B$.$ This demonstrates mapping reduction, where a basic function connects membership of strings in one language to another.