Пошаговое объяснение:

№1

1 - 3/7 = 7/7 - 3/7 = 4/7

1 + 1/6 = 1 1/6

2 - 11/12 = 1 12/12 - 11/12 = 1 1/12

4 3/10 - 3 7/15 = 4 9/30 - 3 14/30 = 3 39/30 - 3 14/30 = 25/30 = 5/6

№2

а)

1 - х = 1/10 + 4/15

1 - х = 3/30 + 8/30

1 - х = 11/30

х = 1 - 11/30

х = 30/30 - 11/30

х = 19/30

б)

х + 1 3/8 = 2 3/4 + 5/16

х + 1 6/16 = 2 12/16 + 5/16

х + 1 6/16 = 2 17/16

х = 2 17/16 - 1 6/16

х = 1 11/16

№3

1) 13 5/12 + 1 3/4 = 13 5/12 + 1 9/12 = 14 14/12 = 15 2/12 = 15 1/6 (км/ч) - скорость лодки по течению

2) 13 5/12 - 1 3/4 = 13 5/12 - 1 9/12 = 12 17/12 - 1 9/12 = 11 8/12 = 11 2/3 (км/ч) - скорость лодки против течения