1. -2y-20=6y+28
-28-20=6y+2y
-48=8y
y=
y=-6
2. -21-1,5y=36,2+3,7y
-1,5y-3,7y=36,2+21
-5,2y=57,2
y=
y=-11
3. 1/5y+7=20-1/20
1/5y=20-1/20-7
1/5y=13-1/20
0,2y=12,95
y=64,75
4. 8*(6+x)-4x=5x-60
48+8x-4x=5x-60
4x-5x=-60-48
-x=-108
x=108
Подробнее - на Znanija.com - https://znanija.com/task/35333206#readmore