Numbers were written as many times as was necessary to make up the full number. Emphasis was always on laying them out as neatly as possible.
The Egyptians only used addition and subtraction and didn't use abstract theorems to calculate their numbers, instead they used tangible everyday objects - such as the number of bricks that will be needed, how much will be needed to fill a jar, etc. These objects were standardize at a very early date so would supply accurate results for the Egyptians.
They had no concept of zero but did use fractions (written by using an 'R' with a number under it i.e. 1/... )