Find Fianos age

Question

Fiona is twice as old as Tessa. Seven years ago, the sum of their ages was 31. Find Fiona’s age now.

Answer 1

We know that Fiona is twice the age of Tessa so we can create the equation: F=2T

 

We also know that 7 years ago the sum of their ages was 31. Since it was seven years ago for both people, that means we would take 7 years off of each of their ages, making the total that we take off 14, giving us the equation:           F+T-14=31

 

In our second equation we will find out what T is all by itself so we can substitute. We will get: T=45-F

 

Now we substitute: F=2(45-F)

 

Distribute the 2: F=90-2F

 

Get the F's on one side: 3F=90

 

Divide by 3 to find F: F=30

 

So Fiona is 30 years old.