Пошаговое объяснение:

3) 1/24

1. - 36/60 * (-5/18) = 1/6

2. (-21/56) * (-1/3) = 7/56 = 1/8

3. 1/6 - 1/8 = 4/24 - 3/24 = 1/24

4) 1/56

1. 9/16 : 21/26 = 9/16 * 26/21 = 39/56

2. 5/7 - 39/56 = 40/56 - 39/56 = 1/56