1.x=3/4-2/5=0.75-0.4=0.35
2.3x=9 所以x=3
3.0.5x=24.5 x=24.5乘以2=49
4 8x=400+32乘以5 = 560 所以x=560/8=70
5 同时乘以36,20+27x=33 ,x=13/27
6.7x=3/4+1/8=7/8 ,x= 1/8
7.同时乘以6,x=63
8.7/12乘以x=4/5乘以5/8= 1/2 ,x=6/7