Short Answer 
The problem involves defining Julia’s age as ‘a’ and Wendy’s as ‘2a,’ while the father’s age is ‘b.’ Using the relationships established, the equations can be solved to determine that Julia is 5 years old and her father’s age is 50.
Step 1: Define Variables
To solve the age problem, we first need to define our variables clearly. Let’s designate Julia’s age as a years. Since Wendy is twice Julia’s age, we can express her age as 2a years old. Lastly, the father’s age is defined as b years old.
Step 2: Set Up Equations
With our variables defined, we must create equations based on the information provided. We understand two key relationships: the father is currently five times Wendy’s age (b = 10a) and in four years, he will be six times Julia’s age ((b + 4) = 6(a + 4)). Setting these up gives us two equations to work with.
Step 3: Solve the Equations
Now, we can solve the system of equations derived from Step 2. First, substitute b = 10a into the second equation to get 10a = 6a + 20. Simplifying this leads to a = 5, which is Julia’s age. Finally, substituting a back into the equation for b, we find the father’s age is b = 10a = 50.