А) 3x+7x+18=178
(3+7)x+18=178
10x+18=178
10x=178-18
10x=160
x=160:10
x=16
б)6y-2y+25=65
(6-2)y+25=65
4y+25=65
4y=65-25
4y=40
y=40:4
y=10
в) 7z+6z-13=130
(7+6)z-13=130
13z-13=130
13z=130+13
13z=143
z=143:13
z=11
г) 21t-4t-17=17
(21-4)t-17=17
17t-17=17
17t=17+17
17t=34
t=34:17
t=2