21 biscuit cards - 7 different biscuits represented as a single biscuit, two biscuits and three biscuits. 
Pair with the ‘Money Cards’ to play Biscuit Algebra. 
Pick two biscuit cards and a money card at random. Now find two amounts that equal the total. 
For example, if you pick two biscuits and then three biscuits, the first amount must be divisible by two and the second amount must be divisible by three. See last photo for an example.