Write a ratio as a fraction in simpliest form : 12 girls in a class of 28 students

12/28 is equal to 3/7 (divide both the numerator and the denominator by the highest common factor).

You first start with the ratio:
12:28

Now you see what goes in it, seems like 2, because it's an even number.
12 / 2 = 6
24 / 2 = 12

6:12 can still be divided.
6 / 2 = 3 
12 / 2 = 6

3:6 is the final product, now we have to turn it into a fraction.

3 is half of 6 so we could turn it into a one and a half fraction.
1/2

Our final product will be 1/2.

Hope this helps!~