Question 739847
Let x = supplment of angle 4y


The two angles must add to 180 since they are supplements, so


x+4y = 180


x+4y-4y = 180-4y


x+0y = 180-4y


x+0 = 180-4y


x = 180-4y


x = -4y + 180


So the final answer is <font color="red">-4y + 180</font>