3/4X减1/2X等于9/4（3/4减1/2）X等于9/4（3/4减2/4）X等于9/41/4X等于9/4X等于9/4除以1/4X等于9
:3/4×减1/2×等于9/4，也就是1/4x=9/4x=9
3/4x-1/2x=9/4（3/4-1/2）x=9/41/4x=9/4x=9/4÷1/4x=9
3/4X－1/2X=9/4(3/4－1/2)X=9/41/4X=9/4X=9
