a) 5x-15 = 0
5x = 15
x = 15:5
x = 3
b) 4x+16 = 20
4x = 20-16
4x = 4
x = 4:4
x = 1
c) -3x+11 = -1
-3x = -1-11
-3x = -12
x = (-12):(-3)
x = 4
d) -2x-200 = 0
-2x = 200
x = 200:(-2)
x = -100
e) 21 = 7x-21
7x = 21+21
7x = 42
x = 42:7
x = 6
f) 10x+99 = 88
10x = 88-99
10x = -10
x = -10:10
x = -1
g) 2x+x = -20+(-10)
3x = -30
x = -30:3
x = -10
h) -(1-2x) = -37
-1+2x = -37
2x = -37+1
2x = -36
x = -36:2
x = -18