you know (hopefully) the formula for the future value in terms of interest, annuity amount, number of periods.

in principle this gives you an equation you can solve for the interest rate. However this is a polynomial of degree n, and i know of no general formula for the result. Unless you have been taught how to solve polynimials of the relevent size you will need to use numerical methods.

it is easy to show that i is the IRR of the annuity so you can use whatever numerical method you were taught to calculate an IRR.