Answer: You bought 3.5 pounds.
Step-by-step explanation: Okay so it costs $12 to get two pounds of jelly beans. You divide 12 by 2 and end up getting 6. You then divide 21 by 6 and get 3.5 because each pound is 6. 2 pounds is 12, and 3.5 pounds is $21. I hope this helped! :P