Even though you've already chosen a "Best Answer" for this, I felt compelled to provide the real answer...
The problem says you deposit $50 A MONTH, e.g. 420 $50 deposits, NOT one $50 deposit. This is a Future Value ordinary annuity problem
FVoa = PMT [((1 + i)n - 1) / i]
n = 35 * 12 = 420
i = 0.09 / 12 = 0.0075
FVoa = 50[((1.0075^420) - 1) / 0.0075]
= 50[22.06338 / 0.0075]
= 50[2941.78]
= $147,089.22
Notice that "Twilights" answer doesn't even equal the total of the monthly deposits...
50 * 420 = $21,000
His/her answer is simply the future value of ONE $50 deposit.
Future values with monthly compounding
Suppose you deposit $50 a month into an
account that has an APR of 9%, based on
monthly compounding, how much will you have
in the account in 35 years?
