Question

A person invests 8000 dollars in a bank. The bank pays 6.5% interest compounded quarterly. To the nearest tenth of a year, how long must the person leave the money in the bank until it reaches 10500 dollars?
oobleck
no steps, just the usual formula:

8000(1 + 0.065/4)^(4x) = 10500
zdenka
4.2175 rounded to 4.2