1)5х-20=x+8
5x-x=20+8
4x=28
х=28:4
х=7;
2)9-7х-21=5-6х
-12-7х=5-6х
-7х+6х=5+12
-1х=17
х=17:(-1)
х=-17;
3)7х+9-11х+7=8
-4х+16=8
-4х=8-16
-4х=-8
х=-8:(-4)
х=2;
4)19,6+y=8,4-7y
y+7y=8,4-19,6
8y=-11,2
y=-11,2:8
y=-1,4;
5)2,4-1,6y=3,5-1,5y-1,9
-1,6y+1,5y=3,5-1,9-2,4
-0,1y=-0,8
y=-0,8:(-0,1)
y=8;
6)1/8x-1/4=2x-23/2
1/8x-2x=1/4-23/2
1/8x-16/8x=1/4-46/4
-15/8x=-45/4
x=-45/4:(-15/8)
x=6/1
x=6