Question

find the measure of angle x, in degrees.
a 40
b 120
c 80
d 100

Explanation:

Step1: Use the exterior - angle theorem

The exterior - angle theorem states that an exterior angle of a triangle is equal to the sum of the two non - adjacent interior angles. Let the exterior angle be \(140^{\circ}\), and the two non - adjacent interior angles be \(x\) and \(60^{\circ}\). So, \(x + 60=140\).

Step2: Solve for \(x\)

Subtract \(60\) from both sides of the equation \(x + 60=140\). We get \(x=140 - 60\).

Answer:

\(x = 80\), so the answer is C.