This problem is an example of ratio and proportion. A ratio is a comparison between two different things. You are given the height and weight of a man at 6 feet and 165 pounds. Also you are given 5 ½ feet. You are required to find the weight of the man at 5 ½ feet. So,
6 feet/165 pounds = 5 ½ feet/ weight
Weight = 5 ½ feet/ (6 feet/165 pounds)
Weight = 151.25 pounds