In Mrs. Julie's classroom the ratio of boys to girls is 12 to 8.
If the entire elementary school has a population of 400 students, how many would you expect to be girls?
12/8 = 3/2 = boys/girls
boys/total = 3/5
girls/total = 2/5
so that boys/girls = 3/2
so girls /total = 2/5 = girls/400
girls = 800/5 = 160