x+40%=140
x=140-40%
x=139.6
7x+500%=75
7x=75-500%
7x=70
x=10
48-20%x=28
20%x=48-28
20%x=20
x=100
75%x=90
x=120
75%x=150
x=200
(x-40)%=0.2
x%-40%=0.2
x%=0.6
x=60
(4.5-50%)x=180
4x=180
x=45