If you are looking for the answer in the format of Y = Mx + b then keep reading...
1) we have to get the Y by itself so we subtract 4x from both sides... the equation now will look something like this---> 3y= -4x + 39
2) now in order to get Y completely by itself we divide the 3 from the Y by rest of numbers... to get something like 3y/3= -4x/3 + 39/3
3) now Y is by its self and the new equation will be----> Y = -4/3 + 13