Arabic
Europeans use the roman alphabet for writing, and Egyptians use the arabic alphabet. For numbers, though, it's not so simple. Until the 16th century, most Europeans used roman numerals, so eight would be written VIII. Since then, Europeans mostly use a decimal system based on a mixture of Hindu and Arabic digits. This is what the European and Arabic digits look like:
As you can see, the one and the nine are the same: the rest of the European digits come from the Hindu numbering system. For both European and Arabic numbers, the most important digits are at the left- so from left to right, the digits are hundreds, tens then units. Arabic numbers are a lot easier to learn than arabic writing: if you live in an arab country, it is well worth while learning arabic numbers even if you don't intend to learn the alphabet.
It's not completely straightforward, though. Take another look at the handwritten arabic: it's a bit confusing, because the handwritten 3 looks a lot like the printed 2. To confuse matters further, some people hand-write numbers the way they are printed, so you have to know somebody well, or look for other examples of twos and threes in the same document, to be able to work out which is which. As an example, here is a telephone number written in arabic: see if you can work out what the number is.
For more information about arabic numbers and how they fit into the language, see Grammar: numbers.
Why don't Europeans use Roman numerals any more? That's quite simple: the hindu-arabic system is a lot easier to do sums with. The Arabs originally used a system based on vertical bars, but in about 800AD Persian mathematicians started using the hindu system. Once they published explanations about how to do arithmetic using the hindu system, its popularity grew and its usage spread.
Western scientists and mathematicians were in contact with arab academics through the muslim university in Cordoba. They learned about the new system in the 12th century, but Europe was going through a bad time (the dark ages). Furthermore, the new numbering system was forbidden in Italy until the end of the 13th century and was not widely accepted until the 15ht century.
The hindu-arabic system did not become widely known until the Renaissance in the 15th century. By this time, printing was gaining in popularity and the style of european writing was starting to be adapted for printing. When the new numbering system got this treatment, some of the arabic digits were considered unsuitable, so some of the hindu digits were used to replace them, and the digits were then adapted to further improve readability.
Mike Green 27Dec2015