Answer:
15
Step-by-step explanation:
(-7,0) and (8,0) are on the opposite side of origin of x axis
d = 8 - -7 = 15
 
        
             
        
        
        
The area is 20
The height is 5
The volume is 60
The surface area is 94
        
             
        
        
        
F = 18 ft.
The law of cosines states 
c² = a² + b² - 2ab cos C
Using our information, we have 
c² = 23² + 16² - 2(23)(16)cos 52
c² = 529 + 256 - 736cos 52
c² = 785 - 736cos 52
c² = 331.8732
Taking the square root of both sides, we have
c = √331.8732 = 18.22 ≈ 18
        
             
        
        
        
Knowing the interior angle sum formula is; 
180x(n-2)
180x(n-2)=1260 (solve for n here) 
180n-360=1260 
180n=1260+360
180n=1620 
n=1620/180 
n=9
Therefore, this polygon has 9 sides.
Hope I helped :)