Chapter 7: Anything but the Evil Wizard of Math! And a Difficult Problem to Solve...

Norman looked at the remaining students with an evil look in his eye. Then they all yelled, "Give us Hannah and David back. Give us David and Hannah back!"
"Never!" yelled Norman.
"You horrible little man, we're going to tell Mr. R. if you don't give them back!" yelled Serena.
"Well," said Norman, "I know Mr. R. loves math problems so maybe I will make a little math riddle to see if you'll get your friends back."
"What's the riddle?!" yelled Justin.
"This is the riddle, good luck," laughed Norman as he handed them a sheet of paper with questions on it. It said something a little bit like this:
Solve the following two problems and then find the difference between the two answers.
The difference is equal to the number of students that I am going to let you have back before I go.