Question

{Given A={2,3,4}, B={2,5,6,7}. Construct an example of the following

A mapping from B to A, which is many one.

Answer 1

A mapping from B to A is many one if two distinct elements of B have the same images in A.
Given $A=\{2,3,4\},B=\{2,5,6,7\}$

So, $g=\left\{\right(2,3),(5,2),(6,3),(7,4\left)\right\}$ or $g=\left\{\right(2,4),(5,2),(6,3),(7,4\left)\right\}$ or $g=\left\{\right(2,2),(5,2),(6,3),(7,4\left)\right\}$.....

i.e. distinct elements of B have the same images in A.