The row for month 25 shows that after <em>twenty-five payments</em> <u>the balance of the loan is $10,356.03</u>
You are told that the<em> loan amount or principal is $ 19,900</em>.
From those two data, you can calculate <em>how much of the principal has been paid off after </em>25 months, because the amount paid off is equal to the loan less the balance after 25 payments:
Principal paid off = $ 19,900 - $ 10,356.03 = $9,543.97
, what is the area of the triangle.
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