1、（31分之25*x-20）*1又5分之4=x＋202、40x+90*（9-x）=6103、90-3x=2*（48-3x）4、3x-17=x+305、4分之1*（X+90-42）=X-18

1. (25x/31-20)×1又4/5＝x+20.
(25x/31-20)×9/5＝x+20.
45x/31-36＝x+20.
14x/31＝56
x＝124.
2.40x+90(9-x)=610
40x+810-90x=610
-50x=-200
x=4.
3.90-3x=2(48-3x)
90-3x=96-6x
3x=6.
x=2.
4.3x-17=x+30.
2x=47.
x=47/2.即二分之四十七
5. (x+90-42)/4=x-18.
x+90-42=4(x-18)
x+48=4x-72.
-3x= -120.
x=40.

1·25/31x*9/5-20*9/5=x+20
45/31x-x=20+36
14/31x=56
x=56*31/1x=124
2.40x+810-90x=610
90x-40x=810-610
x=200/50
x=4
3.90-3x=96-6x
3x=6
x=2
4.3x-x=30+17
2x=47
x=23.5
5.1/4x+1/4*48=x-18
x-1/4x=12+18
x=30*4/3
x=40