My answer choices are 100, 120, 142 & 1200, but when I try to estimate I don't get any of those answers. I try to change 6432 to 6400 and 45 to 50 and get 128, but I only get 120 if I change 6400 to 6000 and 45 to 50 but I don't know if that is correct, when the actual answer is 142.9