5/7×21/15:9/24
4/5:8/10:20/2

Пошаговое объяснение:

1.

1) 5/7 * 21/15 = 1/1 * 3/3 = 3/3 = 1

2) 1 : 9/24 = 1 * 24/9 = 24/9 = 8/3 = 2. 2/3

2.

1) 4/5 : 8/10 = 4/5 * 10/8 =

1/1 * 2/2 = 2/2 = 1

2) 1 : 20/2 = 1 * 2/20 = 2/20 = 1/10