1)
3x-15 = x+3
3x-x = 3+15
2x = 18
x = 18:2
x = 9
2)
7-3x = x+11
-3x-x = 11-7
-4x = 4
x = 4:(-4)
x = -1
3)
2(x+3) = x+13
2x+6 = x+13
2x-x = 13-6
x = 7
4)
4(5-x) = 3x-1
20-4x = 3x-1
-4x-3x = -1-20
-7x = -21
7x = 21
x = 21:7
x = 3
5)
3(x-2) = x+4
3x-6 = x+4
3x-x = 4+6
2x = 10
x = 10:2
x = 5
6)
5(x-1) = 4x+3
5x-5 = 4x+3
5x-4x = 3+5
x = 8