I take a loan in the amount of 3500 HRK which I pay 75 HRK per month with a 3% interest on the remaining debt. When will I pay him back?

Question

I take a loan in the amount of 3500 HRK which I pay 75 HRK per month with a 3% interest on the remaining debt. When will I pay him back?
My attempt:
The formule that I was given to me was this: $$D_n = \text{debt after n mounths}$$ $$D_n=D_{n-1}\cdot(1,03) - 75$$ $$D_0=75$$ When I calculate this I see that debt is rising???
3500
3560.9
3592.727
3625.50881
3659.274074
3694.052297
3729.873865
3766.770081
3804.773184

Answer 1

It's a little less than 50 mos.

>>> d = 3500
>>> def f(x): return x*1.0025 - 75
... 
>>> for k in range(40):
...     d = f(d)
... 
>>> d
716.6252315796193
>>> for k in range(10):
...     d = f(d)
... 
>>> d
-23.750234049532082
>>>