Пошаговое объяснение:

№3

1) 5/6 * 3/20 = 1/2 * 1/4 = (1*1)/(2*4) = 1/8

2) 3/7 * 6/11 = (3*6)/(7*11) = 18/77

3) 10/11 * 11/26 = 5/1 * 1/13 = (5*1)/(1*13) = 5/13

4) 19/42 * 21/38 = 1/2 * 1/2 = (1*1)/(2*2) = 1/4

5) 3/4 : 33/20 = 3/4 * 20/33 = 1/1 * 5/11 = 5/11

6) 25/72 : 45/63 = 25/72 * 63/45 = 5/8 * 7/9 = (5*7)/(8*9) = 35/72

7) 8/15 : 24 = 8/15 * 1/24 = 1/15 * 1/3 = (1*1)/(15*3) = 1/45

8) 8 : 4/5 = 8 * 5/4 = (8*5)/4 = 40/4 = 10

9) 2/3 * 6/7 : 4/7 = 2/3 * 6/7 * 7/4 = 2/3 * 3/1 * 1/2 = 2/3 * 3/2 = 1/1 * 1/1 = 1/1 = 1

10) 11/12 : 7/24 * 21/22 = 11/12 * 24/7 * 21/22 = 11/1 * 2/7 * 21/22 = 22/7 * 21/22 = 1/1 * 3/1 = 3/1 = 3