London is stored so-called papyrus Ahmes which is about 4 thousand years. It is called "Instruction about how to reach the knowledge of all dark (hard) things, all the secrets that hide things... the Scribe (official) Ahmes wrote this... from old manuscripts and is a regular collection of problems with solutions. This papyrus is sometimes called the papyrus Rind (the so-called English collector who bought this "book" more than a hundred years ago).
In the papyrus there are challenges that we are now solved with the help of equations. To denote an unknown number the Egyptians used a special symbol, called "AXA" ("heap").
If you want, you can try to solve one problem from the papyrus of Ahmes. Here's her condition: "Pile. Her seventh part of its whole. That is 19" translated Into English, it would sound like this: "Find the number which, when folded his seventh part, will give in the amount of 19".
X + X/7 = 19