I didn’t see an image or anything but I looked it up and it said regular polygons, since they have the sides all the same length they must always be in the same proportions, and their interior angles are always the same.
        
             
        
        
        
Answer:
Each book weighs 2.5 pounds.
Step-by-step explanation:
75/2.5 is 30.  Or you could also get the answer by 30* 2.5 which it would be 75. So, therefor, the answer is 2.5.
 
        
                    
             
        
        
        
Answer:51 Groups
Step-by-step explanation:
60 students + 42 students = 102 
102 divided by 2 = 51 Total groups.
 
        
             
        
        
        
I think, not 100% sure, but I think it is square root (A/4pi)=r