First, you would subtract the amount of tax placed on the original price of the house to only have the original price of the house left over. Then, you would find 1/25, or 4%, of the original price of the house to find out how much Percy earned. After you have found out how much Percy earned, you would subtract Percy's commission from the original price of the house. The amount left over would be how much money the agency made on this sale.
230,000
18,000
-_______
$212,000
1 4
----- = ------- = 4%
25 100
4
------------ = 0.04 x 212,000 = $8,480
212,000
212,000
8,480
-_______
$203,520
The agency made $203,520 on the sale.