x+y=17①(1-1/5)x=y+1②由①得x=17-y③把③代入②得4/5(17-y)=y+1y=7x=10
x+y=17x×(1-1/5)=y+1x=10y=7
x+y=17(1-1/5)x=y+1
X-X*1/5=Y+1X+Y=17
X+Y=17(4/5)X=Y+1