The Roman numeral XIX is the number 19. X is the number 10, and I is the number one. When a lower number is placed in front of a larger number, it indicates subtraction; IX is the same as 10 minus one, which equals nine.
The Ancient Romans used different letters to represent numbers. In the Roman number system, V is five, and L is 50. C is 100, which comes from the Latin word "centum" for 100. The letter D is 500, and M is 1,000. Lower numbers are added to higher numbers when they follow them in a sequence. For example, VIII means the number eight.