For this algebraic problem, you have to assign variables so you can formulate equations to help you solve the problem. Let x be the age of Jan, y be the age of Betty and z be the age of Joe. You are to find the value of z. The equations would be:
x = 2y and x = 0.5z
Equating this two yields 2y = 0.5z. There are two variables but only one equation. Therefore, you have to specify one of the variables to be able to solve this problem. It was mentioned that Betty just got married. Let's assume that Betty's age was around 30 years old. Then, it follows that y=30. Substituting this to the final equation,
2(30) = 0.5z
z = 120 years old
This is impossible. Betty must have been married at an early age. Let's assume that Betty is 18 years old, then
2(18) = 0.5z
z = 72 years old
If Betty was 18 years old, then Joe is 72 years old. This is only an illustration to the problem. You must have introduced Betty's age to know the exact answer for Joe's age.
