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