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