x ÷ ( 4x/3 ) = x/4
x · 3/4x = x/4
3/4= x/4
3/4 · 4 =x
x=3
x除以4x/3 = x乘以3/4x
约掉x
= 3/4
得出 3/4 = x/4
左右两边同乘4
得x=3