This is a GREAT way to let kids work on their math skills (addition, subtraction, multiplication, and division) by creating equations that have to equal 20 using mystery numbers in a set amount of time! My students beg to play this! The download comes with instructions and ways to bump it up in difficulty to make it more challenging. It encourages creative thinking, a thorough understanding of math processes, and good computational skills. It can be used for the whole class, small groups, and centers.