*the ratio of boys to girls was 3 to 7. If there were 200 more girls than boys in 2012, how many boys were enrolled that year? *

In any group of 10 children, 3/10 are boys, and 7/10 are girls.

In a group of 10 children, there are 4 more girls than boys.

" " " " 100 " , " " 40 " " " "

" " " " 500 " , " " 200 " " " "

So, there were 500 children enrolled in 2012.

7/10 of these children were girls, and 7/10 of 500 = 7*50 = 350

And, of course 3/10 of these children were boys, and 3/10 of 500 = 3*50 = 150.

And 350 - 150 = 200, the number of girls more than boys.

**Answer: in 2012, 350 girls were enrolled.**