Two angles are supplementary and one of the angles is five times the smaller angle, what is the measure of the larger angle

Let x be the bigger angle 
y the smaller angle

x + y = 18   supplementary

x = 5y 

we replace quation 2 in equation 1 so 

5 y +y =180
6y = 180
y= 30 

and x= 5y = 5*30 = 150