The angle sum property of a triangle :
- The sum of the interior angles of a triangle is 180°.
- This property of a triangle is true for all triangles.
So ,
[tex] \begin{cases}\large\bf\red{ \longrightarrow} \rm \:x \: + \: x \: + \: x \: = \: 180 \degree \\ \\ \large\bf\red{ \longrightarrow} \rm \:3x \: = \: 180 \degree \\ \\ \large\bf\red{ \longrightarrow} \rm \:x \: = \: \cancel\frac{180}{3} \\ \\ \large\bf\red{ \longrightarrow} \rm \:x \: = \: 60 \degree \end{cases}[/tex]
