One way to attack this problem is to list F1 to F11: 10, 13, 16, 19, 22, 25, 28, 31, 34, 37, 40. Notice that F6 through F10 are included in both quantities, so focus on what’s different. Quantity A is F4+F5 and Quantity B is F11. Quantity A is 19 + 22 = 41, and Quantity B is 40. Alternatively, you know that F4 has had 3 changes from F1. So, F4 = F1 + 3(3) = 10 + 9 = 19. F5 has had 4 changes from F1, so F5 = F1 + 3(4) = 10 + 12 = 22. F11 has had 10 changes from F1, so F11 = F1 + 3(10) = 10 + 30 = 40.