120/с=4 с*9=810 с/8=60 а/5=50 810/а=9 7*b=490 b*4=320 b/9=90 450/a=9"

1)

120/c = 4

c = 120 / 4

c=30

2)

9c = 810

c = 810/9

c = 90

3)

c/8=60

c = 60 * 8

c = 480

4)

a/5 = 50

a = 50*5

a=250

5)

810/a=9

a=810/9

a=90

6)

7b=490

b=490/7

b=70

7)

4b=320

b=320/4

b=80

8)

b/9=90

b=90*9

b=810

450/a=9

a=450/9

a=50