Ответ:

1-ое задание А:

1/3+1/6=1²/3+1/6=2/6+1/6=3/6=1/2

1/2+1/3=1³/2+1²/3=3/6+2/6=5/6

3/5-1/10=3²/5-1/10=6/10-1/10=5/10=1/2

1-ое задание Б:

1/3-1/6=1²/3-1/6=2/6-1/6=1/6

3/20+3/4=3/20+3⁵/4=3/20+15/20=18/20

7/9-2/3=7/9-2²/3=7/9-4/9=3/9=1/3

1-ое задание В:

11/20-5/12=11³/20-5⁵/12=33/60-25/60=8/60

8/9+7/54=8⁶/9+7/54=48/54+7/54=55/54=1 1/54

5/6-17/21=5⁷/6-17²/21=35/42-34/42=1/42