Answer:
∠ AOB = 139°
Explanation:
Since AOC is a straight line then
∠ AOB + ∠BOC = 180° , that is
8x + 51 + 6x - 25 = 180
14x + 26 = 180 ( subtract 26 from both sides )
14x = 154 ( divide both sides by 14 )
x = 11
Then
∠ AOB = 8x + 51 = 8(11) + 51 = 88 + 51 = 139°