Answer: 17.25 lbs.
Explanation: If Charlotte uses 1/5 of the bag, she has used 10 lbs., since 1/5 of 50 is 10. This leaves 40 lbs. in the bag. If she gives 22.75 pounds to her her friend, then to solve all you have to do is subtract 22.75 from 40. This leaves 17.25 pounds of dog food in the bag.