<span>(631-478)*y=772
153*y=772
y=772:153
y = 5 7/153
</span>
X-20=40
x=60
Сделала корокто
1) 2х + 4 ( 40 - х ) = 100
2х + 160 - 4х = 100
2х - 4х = 100 - 160
- 2х = - 60
- х = - 30
х = 30
2) 4х + 2 ( 40 - х ) = 100
4х + 80 - 2х = 100
4х - 2х = 100 - 80
2х = 20
х = 10