Take the digits 4 5 6 7 8 and 9. Make any three numbers each with 8 digits. Put commas for easy reading.

Prove that if x and y are odd positive integers then x² – y² divisible by 4.

Prove that exactly one out of every three consecutive integers is divisible by 3.

A tailor needs 18m of cloth to stitch 9 shirts of the same size. How much cloth will he need to stitch 15 shirts?

Write five situations for the following where brackets would be necessary.

(a) 7(8 – 3)

(b) (7 + 2) (10 – 3)