please help with this question

Step-by-step explanation:
m< AOC = 90°
m< AOB +m<BOC = 90°
6x-12+3x +30 = 90°
9x +18° = 90°
9x = 90- 18° = 72°
x = 8°
m<AOB =6(8)-12 = 48-12 = 36°
Since, OA is perpendicular to OC
[tex] m\angle A OC= 90 \degree \\ m\angle AOB \: + m\angle BOC = 90 \degree \\ (6x - 12) \degree + (3x + 30) \degree = 90 \degree \\ 6x + 3x + 30 - 12 = 90 \degree \\ 9 x + 18 = 90 \\ 9x = 90 - 18 \\ 9x = 72 \\ x = \frac{72}{9} \\ x = 8 \degree[/tex]
[tex] m\angle \: AOB = 6x - 12 \\ m\angle \: AOB = 6(8) - 12 \\ m\angle \: AOB = 48 - 12 \\ m\angle \: AOB = 36 \degree[/tex]