Basic triangle plane geometry problem - impossible?

[rieuk]

Consider a point P inside a triangle ABC. Angle PBC is 10 degrees, angle PCB is 20 degrees, and angle BAC is 100 degrees. Find angle PAC.

Question is that is this problem even solvable? I found it in an Olympiad training book...

 

[tiny-tim]

hi rieuk!

no, A could be anywhere on an arc of a circle, so PAC could be anything between 0° and 100°

 

[rieuk]

That's what I thought! Cheers!