So the question is comparing 2 different scenarios. It also says that both distribution of weights are approximately equal. So now all you have to do, is find in how many standard deviations from the mean does the boys weight lie, 9.1 pounds. Then find the z-score for the value 9.1. Then you're going to have the z-score and mean of the whales. Using that, find the value point for a whale that is approximately that z-score.
So :
(9.1 - 7.36)/0.96 = 1.8125
Then use the z score and mean of the whale in the formula :
