140° + ∠5 = 180° <em>same side interior angles </em>⇒ ∠5 = 40°
∠2 ≅ ∠5 <em>vertical angles ⇒ </em>∠2 = 40°
∠8 = 53° <em>alternate interior angles</em>
∠3 ≅ ∠8 <em>vertical angles ⇒ </em>∠3 = 53°
x + ∠2 + ∠3 = 180° <em>triangle sum theorem</em>
x + 40° + 53° = 180°
x + 93° = 180°
x = 87°
Answer: 87°
Note: I just realized that there is an easier way to solve this:
∠9 + 53° + x = 180° <em>triangle sum theorem</em>
140° + ∠9 = 180° <em>supplementary angles </em>⇒ ∠9 = 40°
40° + 53° + x = 180°
x + 93° = 180°
x = 87°
Use whichever solutions makes sense to you.