Your answer is 250,000. There are two ways to do this problem.
1) Solve 500/4 to find out how many sheets of paper you get per every dollar. — Your answer is 125 sheets for $1. Then you multiply that answer by 2000, and get 250,000. Which means you get 250,000 sheets of paper for $2000.
2) You can divide 2000 by 4 & that gets you 500, you can then multiply that by 500 & you will get 250,000.
Hope this helps.