(1/2)x - (3/4)y = 1/2
(1/5)x - (3/10)y = 1/5
multiply the top equation by 2
x - (3/2)y = 1
x = 1 + (3/2)y
replace x in the bottom equation with 1/2 + (3/2)y
(1/5)(1 + (3/2)y) - (3/10)y = 1/5
1/5 + (3/10)y - (3/10)y = 1/5
1/5 = 1/5
when you get something like 2=2 or 7=7 or 1/5 = 1/5 this means the two equations are really the same equation. If you multiply both sides of (1/2)x-(3/4)y=1/2 by 2/5, you get (1/5)x-(3/10)y=1/5. When this happens there are an infinite number of solutions. You can plug in any value for x and get a value for y. There isn't just one solution like these problems normally have.