Simultaneous equations like 𝒚 = 2𝒙 - 1 and 𝒚 = 𝒙 + 1 can be represented graphically. To solve the equations graphically, the two lines 𝒚 = 𝒙 + 1 and 𝒚 = 2𝒙 - 1 are drawn on the same diagram.

Marcus du Sautoy uses combinations of peaches and plums and a set of scales, to show how simultaneous equations can be solved. This method didn’t appear in the West until the 19th century, but had ...