Sets 1 & 2 are relatively easy Math Puzzles with answers. Sets 3 & 4 are more advanced and often include negative numbers and "Order of Operations". These are all ready to project from your computer or print out for your bulletin board. I like to have one projected on the board at the start of every math class and let the students debate the answer before we start the lesson. This really gets the students engaged in math before we even start the class. They can also be used as bonus questions on math quizzes or homework assignments.