Answer :
each month there will be 112% of the previous month so the multiplier is 1.12
basically it's trial and error
after 1 month there will be 50 x 1.12 = 56
after 2 months there will be 50 x 1.12^2 = 63
after 20 months there will be 50 x 1.12^20 = 482
after 25 months there will be 50 x 1.12^25 = 850
after 30 months there will be 50 x 1.12^30 = 1498
this is too many so try lower values
after 28 months there will be 50 x 1.12^28 = 1194
after 27 months there will be 50 x 1.12^27 = 1066
after 26 months there will be 50 x 1.12^26 = 952
basically it's trial and error
after 1 month there will be 50 x 1.12 = 56
after 2 months there will be 50 x 1.12^2 = 63
after 20 months there will be 50 x 1.12^20 = 482
after 25 months there will be 50 x 1.12^25 = 850
after 30 months there will be 50 x 1.12^30 = 1498
this is too many so try lower values
after 28 months there will be 50 x 1.12^28 = 1194
after 27 months there will be 50 x 1.12^27 = 1066
after 26 months there will be 50 x 1.12^26 = 952
Trial and error aren't necessary.
Increasing 12% per month means that at any time,
there are (1.12) x (the number there were a month earlier).
After, say, 'M' months, the number has grown by (1.12)^M power.
We want to know what 'M' has to be so that 50(1.12)^M = 1,000
Divide each side by 50 : (1.12)^M = 20
Take the log of each side: M log(1.12) = log(20)
Divide each side by log(1.12): M = log(20) / log(1.12)
M = 1.301 / 0.0492 = 26.44 months