Question

determine the value of x​

Answer 1

Exterior Angle property of a triangle:

• An exterior angle of a triangle is equal to the sum of its two opposite non-adjacent interior angles.

According to Exterior Angle property

$\begin{cases}\large\bf{\orange{ \implies}} \tt \: x \: + \: x \: + \: 20 \: = \: 120 \\ \\ \large\bf{\orange{ \implies}} \tt \:2x \: + \: 20 \: = \: 120 \\ \\ \large\bf{\orange{ \implies}} \tt \:2x \: = \: 120 \: - \: 20 \\ \\ \large\bf{\orange{ \implies}} \tt \:2x \: = \: 100 \\ \\ \large\bf{\orange{ \implies}} \tt \:x \: = \: \cancel\frac{100}{2} \\ \\ \large\bf{\orange{ \implies}} \tt \:x \: = \: 50 \end{cases}$