Well, one quarter of 20 is 5 (because 20 ÷ 4 = 5).  so, to find 3 quarters, we multiply 5 times 3.
5 × 3 = 15, so 3 quarters of 20 is 15.
        
                    
             
        
        
        
Answer:
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Step-by-step explanation:
 
        
                    
             
        
        
        
the total no of population=1650
13:17 first add the two numbers 13+17=30
then 13/30×y =715 , i make 13 at the numerator because it's males ratio
after that 30/13×13/30y =715 ×30/13
y =715×30/13
y =1650
after u find the total no it's simple to find the no of females 
17/30×1650=935
 
        
             
        
        
        
Daria has 12 to 15 nickels because 3x3=9 but u want to double the amount which would be 12 to 15