9x+2又2分之1=2.5
9x+2.5=2.5
9x=0
x=0
8-4.5x=3又2分之1
4.5x=8-3.5
4.5x=4.5
x=1
2*（x-0.7）=4.8
x-0.7=2.4
x=3.1
0.7*4-5x=0.8
2.8-5x=0.8
5x=2
x=0.4
0.6x+3*2.5=67.5
0.6x+7.5=67.5
0.6x=60
x=100