Here is my formula

I know the values of (M), (P) and (n). I want to know (i). This is a formula for a monthly mortgage payment with interest compounded monthly. I know my monthly payment (M), I know my principal (P) and I know my term in months (n). I don't know (i) my interest rate. (i) is APR/12 if that matters. I get as far as dividing both side by (P) and then I ht a road block.

Formula can also be found at How To Calculate Mortgage Payments - Interest and Mortgage Formula Calculation

Thanks!