How to calculate return vs inflation if I'm re-investing part of the money?

Hi!

I don't live in the US, but this is more of a math advice than a proper investing advice.

Say I have 100'000 BRL and I invest it at 14% yearly using government bonds (the norm in Brazil). I'd get 14'000 BRL a year, or just over 1100 monthly.

However, since inflation is roughly 5% a year, my actual return over inflation is closer to 8500 BRL, or about 700 a month.

Now, say I take half of these 700 BRL and reinvest in the same 14% yearly investment.

How much would this help combat inflation? Is there a formula I can use? Thanks!