[yequalsx]

After a lecture and doing several examples I a majority of my college algebra students couldn't do this problem.

You have a house that you bought for $120,000. You sell the house for $173,000 and the real estate commission is 6%. As the seller of the house you have to pay the real estate commission. The real estate commission is an expense and is not counted as part of your profit from the sale of the house. You have to pay a tax of 30% on the profit from the sale of the house. How much tax is paid?

They just couldn't grasp that the real estate commission was not part of their profit. I got the impression that the students believe that the real estate commission is not an expense.

I do believe that a large percentage of society does not understand interest.