I believe it would be 160 because if you divide the number of students they surveyed by the amount that said they would attend (48/12) you get 4 then if you divide 4 by the amount of students in total (640/4) you get 160
        
             
        
        
        
Answer:
25, 36, 49 
Step-by-step explanation:
I just listed them down since there aren't many. 
1×1=2 (Smaller than 20)
2×2=4 (Smaller than 20)
3×3=9 (Smaller than 20)
4×4=16 (Smaller than 20)
5×5=25
6×6=36
7×7=49
8×8=64 (Bigger than 50) 
 
        
             
        
        
        
the correct answer is 2.40