This is a trick for people with big families! Before you begin, get the person doing the sum to count up all the aunts, uncles and cousins he or she has. Then:

1. Add the number of aunts and uncles together (say 4 + 5 = 9).

2. Double it (18).

3. Add three (21).

4. Multiply by five (105).

5. Now add all the cousins - say six (111).

6. Take away 15 (96).

Now see the two figures you've arrived at. The one on the left is the number of aunts and uncles, and on the right is the number of cousins.