$100 at 3% interest since 1996
Compounded how often?
If only compounded annually, which is rare these days, the answer is
100*(1.03)^15 = $155.80
assuming the deposit was made on or just before Jan 1, 1996, 15 years ago.
If the interest is compounded monthly (180 times), the answer is
100*(1.0025)^180 = $156.74