math
posted by tracy .
Question: The price of a home is $180,000. The bank requires a 10% down payment. After the down payment, the balance is financed with a 30 year fixed mortgage at 6.3%. Determine the unpaid balance after ten years.
Answer: The unpaid balance after ten years is $136,641.85
I have the answer but I need help figuring out the formula used and the steps taken to get the answer. Please help.

First you have to find the payment.
You did not say, but I will assume that the payments are monthly.
let the payment be p
162000 = p( 1  1.00525^360)/.00525
p = 1002.74
unpaid balance after 10 years
= balance if you had paid nothing  amount of the annuity for 10 years
= 162000(1.00525)^120  1002.74(1.00525^120  1)/.00525
= 136641.30
could be roundoff error on their part, I kept max number of decimals using calculator's memories.