Question

a side of the triangle below has been extended to form an exterior angle of 129°. find the value of x.

Explanation:

Step1: Recall exterior - angle property

The exterior angle of a triangle is equal to the sum of the two non - adjacent interior angles.

Step2: Set up the equation

We know that \(129^{\circ}=x + 109^{\circ}\).

Step3: Solve for \(x\)

Subtract \(109^{\circ}\) from both sides: \(x=129^{\circ}- 109^{\circ}\).
\(x = 20^{\circ}\)

Answer:

\(20\)