supplementary angles add to 180
let x and y represent the two angles
x + y =180°
and if the ratio is 5:4, we can represent the angles by
x = 5a
y = 4a
5a + 4a = 180°
then solve for a
9a = 180°
a = 20°
x = 5(20)
y = 4(20)
so the two angles are
100° and 80°
