Substitution for:

X-5y=10

2x-10y=20

Since you need an isolated variable to use the substitution method, we need to re-arrange one of the equations. This will probably be easiest to do with the first one.

Add 5y to both sides of the first equation.

x=10+5y

Now, in the second equation, put in 10+5y in any spot that has an x.

2 (10+5y) - 10y=20

Distribute the 2 to both numbers in the parenthesis.

20+10y-10y=20

Combine like terms.

20=20

This means that the two equations are actually the same. You can see this if you multiply the whole first equation by 2

2 (x-5y=10)

2x-10y=20, which is the same as the second equation. Therefore, the two equations are actually the same one.