The ancient Romans used a decimal, base 10 system. Numbers though did not have place values, and different powers are represented by different, capital, letters. It was a very basic system, so basic that it did not have a zero. The simplest operations - addition, subtraction, multiplication and division - were hard to perform. Virtually no advances in any part of mathematics were made under Roman rule, and all the discoveries made by the Greeks before Greece was made part of the Roman Empire, were forgotten.
I = 1 V = 5
X = 10 L = 50
C = 100 D = 500
M = 1000 Th number 498 was CCCCLXXXXVIII (400 x 100+ 50 + 4 x 10 + 5 + 3 x 1)