Algebra is a wonderful tool for testing and predicting our understanding of the world. The Xs, Ys and Zs in the algebra mean something real. Algebra lets us take a word description of the world and change it into a mathematical description which is really useful. Clothing designers use algebra to work out how best to cut cloth, engineers use algebra to design cars, boats and aeroplanes and the next generation of medicines customised to our genetic individuality will use algebra. Plumbers and carpet fitters use algebra to work out how to cut pipes or carpets to fit a space.