You can solve for C using the law of cosines.
P, Q, and R are the angles of the triangle and p, q, and r are the lengths of the sides of the triangle opposite of the angles. That means p = 10ft, q = 12ft, and r=5ft. The law of cosines states that:

Since we're looking for the measure of angle P, we would use the first equation,

. Plug the values we have for the sides of the triangle into the equation and solve for P:
The measure of angle P is about 55<span>
°.</span>
I don’t know sorry this app is making me answer questions
So firstly you are given the external angles, to find the internal angles, you do 180-133=47
180-142=38
the internal angles in a triangle add up to 180, therefore it is
47+38=85
180-85=95
because you have to find the external angle=n you then need to take 95 away from 180
180-95=85
so the answer is A