Alex takes out a loan for $2000 at a 5% simple interest rate determine how much money he will need to re-pay in total

That would be $2000 + $2000 (0.05) (t), where t is the number of years. Unfortunately you have not provided a value for t.

Total payback would be $2000 + $2000 (0.05) (t).

This This is the (simple) interest

is the

principal