I need help and here's the "supposed" solution that I think I solved. For her birthday, Leslie's parents gave her $3,452.00 which they put into a savings account that earns 15% interest compounded monthly. When Leslie started college, she withdrew the entire balance of $11,031.00 and used it to pay for tuition. How long was the money in the account?

so this is a compound interest that I've found on IXL and I put the equation like
A=P(1(+/-)r/n)^nt
A=P(1+0.15/12)^12t
so two questions that I have are that did I put it right and what is the solution to it?