Answer:
x = 8
Step-by-step explanation:
Angle sum property of triangle states that the sum of interior angles of a triangle is 180°.
So,
[tex] \rm \longrightarrow 45 \degree + 80 \degree + (9x - 17) \degree = 180 \degree \\ \\ \rm \longrightarrow 125 + 9x - 17 = 180 \\ \\ \rm \longrightarrow 108 + 9x = 180 \\ \\ \rm \longrightarrow (108 - 108) + 9x = 180 - 108 \\ \\ \rm \longrightarrow 9x = 72 \\ \\ \rm \longrightarrow \dfrac{9}{9} x = \dfrac{72}{9} \\ \\ \rm \longrightarrow x = 8[/tex]
