Answer:
Step-by-step explanation:
The tangent lines meet the radii at 90 degrees.
The way the diagram is drawn, the following formula will work
<AOB + <OAC + OBC + 10 = 360
<OAC = 90
<OBC = 90
<AOB + 90 + 90 + 10 = 360
<AOB + 190 = 360
<AOB = 360 - 190
<AOB = 170
