How will you know you have found all the different number
sentences?
Are there any other sums that have the $8$ in them, for
example?
Are there any other addition sums?
Can you make any number sentences with all four numbers?
You could print out these cards.
Andrew decorated 20 biscuits to take to a party. He lined them up and put icing on every second biscuit and different decorations on other biscuits. How many biscuits weren't decorated?