要过程
通分为(28x+24x+21x)/84=73x/84
x/3+x/3.5+x/4=(3.5X4x)/(3X3.5X4)+(3X4x)/(3.5X3X4)+(3X3.5x)/(4X3X3.5)=(14x+12x+10.5x)/42=36.5x/42
找最小公倍数,同时×84
得(28x+24x+21x)÷84
=73/84 x
等号右边没数?
方程两遍同乘42