if x+2=3 what does y equal?
All equations can be written on the form y=ax+b.
Therefore you must rewrite to stand at that form,
x+2=3 => (x+2)-3=3-3 => x+2-3=0 => x-1=0 =>
a=1, there is only one xb=-1, the rest number gave -1
1x-1=y => x-1=y