The statement "X equals 400" indicates that the variable X has a value of 400. In mathematics, this is a simple equation where X is defined to be equal to a specific number. This can be used in various contexts, such as solving problems or representing quantities in equations. In practical terms, if you encounter "X equals 400," it means that whenever you see X in a calculation or formula, you can replace it with the number 400. This concept is fundamental in algebra and helps in understanding relationships between different variables.