Line of intersection of 2 planes FP3

They've expressed y in terms of x separately and in terms of z separately, Go back to lines 4 and 5 and rearrange to make y the subject

You shouldn't :P

Wouldn't it have been easier just to make y the subject in lines 4 and 5 instead of making x the subject then later rearranging for y again?

I tried the question but I made y the subject after adding equation 1 and 2. This approach led me to a different answer. Is this wrong or is there more than one answer?