No more than 74 on average of 5 games means no more than 370 shots on total. If you add all of the numbers up you will get 292, so he can still shoot 370-292=78 in the last round, which is answer choice B.
The answer would be 6x/5-16/5
503 x 3 = 1509
But, it you want to estimate it I would say 1500.
