This is straight forward:
You have already said: y = 2x - 5 ...........(i)
4x - y = 7............(ii)
So anywhere we see, y in equation (ii) we replace it with (2x - 5).
4x - (2x - 5) = 7
4x - 2x + 5 = 7
Note minus sign before the bracket, changes sign inside the bracket.
2x + 5 = 7
2x = 7 - 5.
2x = 2 Divide both sides by 2.
x = 2/2
x =1.
Remember from (i) y = 2x - 5, y = 2*1 - 5 = 2-5 = -3.
Therefore, x = 1, y = -3.
Those are the steps.