First question...does y=x
If so, x=4
Now, plug in 4 wherever you see an x.
Therefore y = 4
If the equation looks like the following, them plug in 4 wherever you see x:
or 3x+5=y (3x means 3 times 4) Always follow pemdas (parenthesis first, then do exponents, then multiplication or division whichever comes first from left to right, then subtraction or addition from left to right.)