What equations do I need to solve these problems about U.S. debt?

Question

The first question is: What is the function that shows the amount of debt per citizen as a function of time? What will the amount of debt per citizen be in 20 years?

The second question is: If the current compound interest rate on our national debt is 8% (compounded annually), what will the national debt be in 5,10,20 years?

I am struggling with finding the equations for these two questions. I think it's exponential but I am not quite sure.

Answer 1

A(t) =Pe^rt where e=about 2.732, r = rate of compounded interest per year and t = number of years, P = the debt at time t=0, A = the debt at time t

plug in 0.08 for r, plug in 5, then 10 and 20 for t, and plug in the current debt for P, A is the future debt, A(5) is the debt in 5 years, A(10) = debt in 10 years, A(20) is the debt in 20 years.