Since a straight line is equal to 180, x+4x=180
The two angles are opposite each other, and therefore will equal 180 together.
5x= 180
Divide both sides by 5.
180/5= 36
x=36
Let's check our answer.
4*36= 144
144+36= 180
The smaller angle is equal to 36, and the bigger one 144.
I hope this helps!
~cupcake