Determine whether the given equation defines y as a function

Determine whether the given equation defines y as a function of x. 3x + 4y = 12

given 3x+4y=12

subtract 3x on both sides

3x+4y-3x=12-3x

4y=12-3x

divide both side with 4

4y/4=(12-3x)/4

y=3-3x/4

therefore y can be writtens as a function of x as y=3-3x//4