30％x+40=80
30%X=80-40
X=40除以0.3
X=400/3
27+3分之2x=54
2/3X=54-27
x=27x3/2
X=40.5
100-30-x=25％x
70-X=25%X
X+25%X=70
1.25X=70
X=70除以1.25
X=56
72-9分之5x=x乘30％
(5/9+30%)X=72
77/90x=72
X=72X90/77
X=6480/77
x+5分之x=240
解;(1+1/5)X=240
6/5X=240
X=240X5/6
X=200