Solution: Take AC as the side, make an equilateral triangle ACE to the right, and connect BE.

So AC=AE=CE

Angle CAE= Angle ACE=60 degrees

Because angle CAB= angle CBA=50 degrees

So CA=CB

Because angle CAB+ angle CBA+ angle ACB= 180 degrees.

So ACB angle =80 degrees

Because angle EAB= angle CAE- angle CAB=60-50= 10 degrees.

Angle OAB= 10 degree

So the angle OAB= the angle AB= 10 degrees.

CE=CB

So angle CEB= angle CBE

Because the angle ECB= angle ACB- angle ACE=80-60=20 degrees.

Angle ECB+ Angle CEB+ Angle CBE= 180 degrees.

So the angle CBE=80 degrees.

Because angle OBA= angle CBA- angle OBC=50 degrees.

OBC angle =20 degrees

So the angle OBA=50-20=30 degrees.

Because angle ABE= angle CBE- angle OBA=80-50=30 degrees.

So angle OBA= angle ABE=30 degrees.

Because AB=AB

So triangle Oba and triangle EBA are congruent (ASA)

So OA=AE

So AE=AC

So angle OCA= angle AOC

Because angle OCA+ angle AOC+ angle OAC= 180 degrees.

Angle OAC= angle cab-angle OAB=50- 10=40 degrees.

So the angle OCA=70 degrees.