解方程 4x+1/5=1/4 9/10x-7/10x=1/100 x除以3/8=2/5

4x+1/5=1/4
4X=1/4-1/5
4X=1/20
X=1/80
9/10x-7/10x=1/100
2/10X=1/100
X=1/100*(10/2)
X=1/5
X/(3/8)=2/5
X=(2/5)*(3/8)
X=3/20