Question

My question is in the comments.

Answer 1

In a system of equations or simultaneous equations, the first step to follow is to make one of the variables the subject of the formula in one of the equations, so that you will insert it in the other equation, being left with only one variable that shall be easily found. As soon as you find that variable, you will re-insert it in the first equation of the simultaneous equations.
For this case, the first equation already has 'y' the subject of the formula, so you directly insert it in the equation and solve for x. Got it?

Answer 2

No I'm still really confused