Well first of you need to know that on a straight line there should be 180 degrees. Also a triangle has 180 degrees in total. Now if this is to scale then you can always measure the angle BCA and explain how you took that away from 180 to get whatever. Assuming otherwise i don't know how one can actually complete this question without any measurements, at least one and it would be something anyone can complete. Even if you didn't have anything it should be a equilateral triangle or isosceles. That way you can work out the inside sides than the exterior. But since it's not, I'm not to sure.
