In this situation I would use cosine to find m∠G.
Cosine = Adjacent side ÷ Hypotenuse
RG being the adjacent side and TG being the hypotenuse, you would set up the equation like this
cos(g) = 8/17
then solve
cos(g) = 0.47058
simplify
g = cos^-1(0.47058)
and you get
m∠G = 61.9°
So your answer would be 62°
