logarithmic and inverse function

Question

You take out a $60,000 school loan. The time (t) in months that it takes to pay off the loan at 9% annual interest with monthly payments of (x) dollars is given by t=133.83ln(x/x-450) estimate the length of the $60,000 loan you will have in order to pay off the loan if your monthly payments are $700

Answer 1

All you need to do is use a calculator, substituting x = 700.  Answer is 173.79 months or about 11 and one half years.

 

I think you need to take ln (700/250); your formula should be 133.82ln(x/(x-450)) to correctly form the denominator.