On your tenth birthday, you received 500 which you invested at 9.5% interest, compounded annually. your investment is worth $2500. how old are you today?

Compounded once a year: A=P (1+r) ^t

2500=500 (1+0.095) ^t

1.095^t=5

because the unknown number is an exponent, use log to find the unknown:

log (1.095^t) = log5

tlog1.095=log5

t=log5/log1.095

use your calculator, t=17.734

so this person is about 28 years old.