Answer:83.0° 
 
Step-by-step explanation: 
 
Given ∆XYZ, with 3 known sides, to find angle X, apply the Law of Cosines, c² = a² + b² - 2ab*cos(C). 
 
For convenience sake, this formula can be rewritten to make the angle we are looking for the subject of the formula. 
 
Thus, we would have this following: 
 
Where, 
 
C = X = ? 
 
a = 8 ft 
 
b = 16 ft 
 
c = 17 ft