I have a loan for a principal amount of \$117,000.00 at 9.75% interest and a total amount due (including the interest for 84 months) of \$191,805.60. I had 84 months to pay it off, or I could pay it off early, without penalties. I have made 61 payments totalling \$139,287.40.
How do I calculate the principal balance due, not including any further interest?