How much will you have in 72 months if you invest $ 125 a month at 12% annual interest?
I = P x R x T
I = 125 x (12/100) x 72/12
I = $90
This is the formula you use to calculate this:
FV=P{[1 + R]^N - 1/ R}. Will assume that your 12% is compounded monthly.
FV = 125{[1 + 0.12/12]^72 - 1 / [0.12/12]}
FV = 125{[1.01]^72 - 1 / [0.01]}
FV = 125 x 104.70993121
FV = $13,088.74