It is absolutely important to look at all the information's given in the question. Those information's would be required to solve the problem.
Amount at which Madison bought the empty plot = $2000
Percentage of profit made on selling = 25%
The amount of profit made by Madison = (25/100) * 2000
= 25 * 20
= 500 dollars
Amount at which Madison sold the empty lot = (2000 + 500) dollars
= 2500 dollars
So Madison sold the empty lot at the rate of $2500. I hope this is the answer you were looking for and the procedure for doing such problems is also clear to you.