If I borrow $26,400 @ 7% interest and make payments of $300 how much will I have left owing after 19 months.
Poor wording
Is the payment made monthly?
Was the first payment made one month after the loan was taken out?
Is the interest compounded monthly?
I will assume those three important facts
i = .07/12 = .00583333...
amount owing after 19 months
= 26400(1.0058333)^19 - 300( 1.00583333..^19 - 1)/.0058333.
= $ 23,475.44
The main reason that your balance is still so high is that the payment of $300 at the beginning is made of over $150 in interest you have to pay each month.
e.g. for the first month the interest would be $154