To find m<A, first you must find it's supplementary angle. In order to do this, you must determine the missing interior angle. We'll call the missing angle x
A pentagon has 540°. Add up the known angles.
96°+118°+115°+104°+x = 540°
433°+x = 540°
x = 107°
Now that we know the value of x, we can find the m<A. Supplementary angles are two angles that add up to 180°, which is a flat line. We can see in the diagram that m<a + 107° is a flat line, meaning m<a + 107° = 180°
