show that graphs of (x-2x)/(x+2y)=1/3 and (x-y)/(x+y)=3/5 coincide...how do you solve it?

You have a typo in the first one

should be
(x-2y)/(x+2y)=1/3
x - 2 y = x/3 + 2 y/3
2 x/3 = 8 y /3
2 x = 8 y

second one
x - y = 3 x/5 + 3 y/5
x - 3 x/5 = y + 3 y/5
2 x/5 = 8 y/5
2 x = 8 y