This activity sheet engages students in using algebra tiles or colored disks to discover the rules for subtraction of signed integers. First, students develop the rules using the color tiles to help them visualize the operation of subtraction. When students try to remove the tiles, they are modeling the operation of subtraction. To be able to subtract discs from what is on the table it is sometimes necessary to add some zero pairs to the table. Zero pairs do not change the value of what is on