3. Peyton is three years younger than Justin. Matt is four times as old as Peyton. If you add together the ages of Justin, Peyton and Matt, the total comes to 39 years. How old are Justin, Peyton, and Matt?

Step 1 ：Let's represent the ages of Justin, Peyton, and Matt with the variables J, P, and M respectively.

Step 2 ：From the problem, we can form three equations: Peyton is three years younger than Justin, which gives us \(P = J - 3\). Matt is four times as old as Peyton, which gives us \(M = 4P\). The total age of Justin, Peyton, and Matt is 39 years, which gives us \(J + P + M = 39\).

Step 3 ：Solving these equations simultaneously, we find that Justin is 9 years old, Peyton is 6 years old, and Matt is 24 years old.

Step 4 ：This solution is consistent with the problem statement: Peyton is three years younger than Justin, and Matt is four times as old as Peyton. The total age of the three is 39 years.

Step 5 ：Final Answer: Justin is \(\boxed{9}\) years old, Peyton is \(\boxed{6}\) years old, and Matt is \(\boxed{24}\) years old.