2x-y/x+y=1/5
5(2x-y)=x+y
10x-5y=x+y
9x=6y
3x=2y
x=2y/3
代入
2x+5y/6x-2y
=(2×2y/3+5y)/(6×2y/3-2y)
=(19y/3)/2y
=19/3×1/2
=19/6