7x-2x=4
5x=4
x=4/5
10.2+2x=11.7
2x=1.5
x=0.75
13除x-5=1.5
13-5x=1.5x
6.5x=13
x=2
3(x-4)=2.1
3x-12=2.1
3x=14.1
x=4.7
(x-0.4)除3=1.02
x-0.4=3.06
x=3.1
x-0.36x=16
0.64x=16
x=25 0.6x+3乘0.5=3.3
0.6x=1.8
x=3
7.5乘3-5x=5
22.5-5x=5
5x=17.5
x=3.5
0.4x除2=1.2
0.2x=1.2
x=6