We know that out of the 28 students 12 of them are boys. To find how many girls there are subtract 12 from 28
28 - 12 = 16
That means that there are 16 girls in the class
Now you need a ratio of girls : boys so...
16 : 12
This can be further simplified to the following...
4 : 3 (C)
This means that for every four girls there are 3 boys
Hope this helped!
~Just a girl in love with Shawn Mendes