You make a down payment of $22,000 and monthly payments of $1800 toward the purchase of a new house. After how many months will your average monthly cost of purchasing the house be $3000, $2500, $1500?
Let this happens after x months.
The total amount paid in those x months = $22000 + 1800*x
Now avg. monthly cost = total amount paid/total no. of months = (1800x+22000)/x = 3000;
Solve for x to get the no. of months.
I got in fraction though (18.333 months)!