An account earning interest compounded annually was worth $44,100 after 2 years and $48,620.25 after 4 years. what is the interest rate?
answer

We let x be the initial amount of money and r be the rate of interest (already in decimal) such that the equation for the future worth of money is,
                        after two years, F = 44100 = x(1 + r)^2
                        after four years, F = 48620.25 = x(1 + r)^4
Solving for the values of x and r in the equation will give us answers of 40,000 and 0.05, respectively. Thus, the interest rate is approximately 5%. 

I’m not sure how this works