Its best to turn fractions into decimals so its easier to solve the problem, in order to do this you would divide the number on the top to the number on the bottom. Ex: 1 divide by 2 So the numerator divided by the denominator. The top of the faction is the numerator and the bottom of the faction is the denominator. So 1 divided by 2 = 0.5 you would replace 0.5 for the 1/2.
Add the 2 values togetehr
Mandy father was 28
Mandy father = 5M=28
M=28/5
Now Mandy will be 28/5+12= 17.6 years
