Ghost Math is a short after Bezt Frends.
Uncle Grandpa takes a child on an adventure through a haunted house. After shooting down several ghosts, Uncle Grandpa has the child work on his math homework pertaining to the amount of ghosts that were in the house. Despite the child arriving at the correct conclusion, Uncle Grandpa believes he is wrong. Unfortunately for Uncle Grandpa, his disbelief in the child lead him to a miscalculation of how many ghosts were still left in the house, so the remaining 4 ghosts attack him and the kid.