Final answer:
To set up the equation for this problem, we consider Paul's current age as x and use the equation (x + 20) = (1/2)((x - 4)^2).
Step-by-step explanation:
To set up the equation for this problem, we need to consider Paul's current age and the information given about his age in the future and the past. Let's represent Paul's current age as x.
According to the information given, in 20 years, Paul will be half the square of the age he was 4 years ago. So, in 20 years, Paul's age will be (x + 20) and his age 4 years ago was (x - 4). We can represent this as the equation:
(x + 20) = (1/2)((x - 4)^2)