Answer:
m<c = 20º
Step-by-step explanation:
We use these following definitions:
The sum of an interior angle with its exterior is of 180º.
The sum of the three interval angles of a triangle is 180º.
The measure of the exterior angle at point B is 100°.
This means that the measure of the interior angle is: 180 - 100 = 80º
m∠A is 4 times larger than m∠c
This means that the measure of angle c is x, and the measure of angle a is 4x. The other angle, B, is 80º. So
The measure of angle C is 20º.