The Monster Who Did My Math

A math-phobic boy faces another dreaded evening of multiplication when a monster suddenly appears in his room and offers him a deal he cannot refuse.
After a quick signature on a contract, the boy’s problems are solved, and his homework is ready to turn in the next day. At first, everything adds up perfectly. But when the boy’s math knowledge is tested at school, his troubles begin to multiply. What did the fine print on that contract read?
In paragraph seven of clause ninety-three,
“If you don’t learn anything, do not blame me!”
When the bill comes, will our hero have the money―and the math skill―to subtract that wicked monster from his life once and for all?