If x represents the number of apples purchased and y represents the number of mangos we can set up the following:
Kayden has $20, so can spend up to this amount:
He must buy a minimum of 16 apples and mangos altogether:
Also, he must buy no less than 16 apples:
We also need to consider y can't be negative, hence add one more inequality:
Plot all four inequalities and see what is the zone of intersection.
The solution is the set of whole coordinates for x and y within the triangle with vertices at (16, 0), (16, 4) and (26.67, 0).
One possible solution is (20, 2) another one (24, 1).
See attached.