I have tried hard to solve, but I'm stuck....

Let’s use our knowledge of quadrantic equations to analyze a real world business application. If P dollars is invested at r rate of interest compounded anually t years, then the amount of money, A, accummulated at the end of t years is given by the formula
A = P (1 + r)t
Barbara invested $100 at a certain rate of interest compounded anually for two years. If the accumulated value at the end of two years is $121, find the rate of interest.