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The number of monthly installments required to get a certain FV =
ln(FVi + cp) - ln(cp)
n = -------------------------
ln(c + i) - ln(c)
FV = future value
p = investment per compound period
i = interest rate
c = # of compound periods per year
n = # of compound periods
..
ln(25000*0.09 +12*200)- ln(12*200) / ln(12+0.09)-ln(12)
88.5 months