Bundle Description90 CARDS + 90 CARDSStatic and dynamic subtraction equation cards with control (equation and control).Back keys allow children to work through problems independently.Cards have color code: ones are green, tens blue, hundreds red, and thousands green.Cards can be used with Montessori materials, such as small and large number cards, golden beads, checker board, bead frames, stamp game OR SEPARATELY.INCLUDES:- 9 sets of different static subtraction level (two, three, four digit and