解方程:X-25%X=30 2X+30%X=9.2 75%X-45%X=12 X+120%X=33

X-25%X=30
0.75X=30
X=30/0.75
X=40
2X+30%X=9.2
2.3X=9.2
X=9.2/2.3
X=4
75%X-45%X=12
0.3X=12
X=12/0.3
X=40
X+120%X=33
2.2X=33
X=33/2.2
X=15