Answer: The answer is 10 watermelons.
Step-by-step explanation: Given that Boris is going to buy pineapples and watermelons, a total of at least 16 fruits with $60 at most. The graph in the question represents the constraints on the number of pineapples P and watermelons W Boris buys.
From the graph, we have for condition A:
Two points are (16,0) and (0,16). So, the first constraint in equation form will be
And the constraint will be
![P+W\geq 16.](https://tex.z-dn.net/?f=P%2BW%5Cgeq%2016.)
Also, from the graph, we have for condition B:
Two points are (20,0) and (0,15). So, the second constraint in equation form will be
And the constraint will be
![3P+4W\leq 60.](https://tex.z-dn.net/?f=3P%2B4W%5Cleq%2060.)
If Boris buy 6 pineapples, then from conditions A and B, we have
![W\geq 10~~\textup{and}~~W\leq 10.5.](https://tex.z-dn.net/?f=W%5Cgeq%2010~~%5Ctextup%7Band%7D~~W%5Cleq%2010.5.)
These will give us that W = 10.
Thus, Boris can buy 10 Watermelons to meet both his constraints.