Пошаговое объяснение:

№15

1) 3 1/2 * 1 1/3 = 7/2 * 4/3 = 28/6 = 14/3

2) 14/3 * 4 5/7 = 14/3 * 33/7 = 2/1 * 11/1 = 22/1 = 22

№16

1) 6/25 * 3 3/4 = 6/25 * 15/4 = 3/5 * 3/2 = 9/10

2) 9/10 * 8/9 = 8/10 = 4/5