Решите уравнение 1) x+4/21=2/3+2/7 2) y+1/4=4/5-3/10 3) (4/5-x) + 13/20=7/10

1)

x+4/21=2/3+2/7

x+4/21=14/21+6/21

x+4/21 = 20/21

x=20/21-4/21

x=16/21

2)

y+1/4=4/5-3/10

y+1/4=8/10-3/10

y+1/4=5/10

y=1/2-1/4

y=2/4-1/4

y=1/4

3)

(4/5-x) + 13/20=7/10

4/5-x=7/10-13/20

4/5-x = 14/20-13/20

4/5-x=1/20

x=4/5-1/20

x=16/20-1/20

x=15/20

x=3/4