Set up a proportion: 
In a sample of 8:7, you have 15 kids in all. 
So the the ratio of girls to kids in a sample of 15 is 7:15. 
So set up a proportion: 
 =
 = 

15x = 1365
x = 91
There are 91 girls.
To find out how many boys there are, we can subtract 91 from 195 and we will get a difference of 104.
Therefore, there are 91 girls and 104 boys.