4/5- 0.8
9/25-0.36
1/10-0.1
7/25-0.28 
You divide the numerator by the denominator  4/5 = 4 divided by 5=0.8
45/ 100 
There are 45 shaded squares , there is a total of 100 squares , the total is the denominator and the numerator is the total of shaded squares .