1. 5x - 3 = 2x + 12
2. 3 (x - 5) = 2 (x - 1)
3. 5x - 6 + 2 (x + 2) = 3x + 7

1. x = 5
2. x = -17
3. x = 2.25
Hope this helped!

Answer

Both are correct.

Explanation
The both equations are the same.
When we say that y=x+10, we can make x the subject of the formula and get;
y=x+10
y-10=x
x=y-10.

If the substitution is done correctly, that is x+10 for y and y-10 for x in the other equation then, both would be correct.