One of the early questions in the NCEES FE Industrial/Systems Exam studyguide has a solution that I can't decipher. The question is as follows:
Bob wants to be a millionaire. To achieve this goal, at the end of the year he invests $5000 each year into an account that pays 10% interest, compounded yearly. How many years will it take Bob to reach this goal?
The part I need help with is the solution to this problem, it's in the image below within the red box. I have no idea how it gets from (5000)((1+0.1)^n - 1)/0.1) to 21 = 1.1^n. Can anyone provide an alternate solution or some explanation? Thank you!