Geometry Practice Test 1

OA = OB = radius
⇒ Δ AOB is an isosceles triangle
⇒ ∠OBA = OAB = 25°
⇒ ∠AOB = 180° −(25° + 25°) = 180° - 50°
∠AOB = 130°

Similarly,
∠AOC = 180° − (35° + 35°)
= 180° - (70°)
∠AOC = 110°
Now ∠AOB + ∠AOC + ∠BOC = 360°
∠130° + ∠110° + ∠BOC = 360°
x = 360° − (130° −110°) = 360° − 240°
x = 120°