Final answer:
The red ant and the black ant are always the same distance from the anthill because they move along parallel lines with the same slope.
Step-by-step explanation:
The red ant and the black ant are always the same distance from the anthill because they move along straight lines that are parallel to each other. The red ant moves along the line y = x, while the black ant moves along the line y = -x. Both lines have the same slope of 1, which means they move at the same rate vertically and horizontally. Therefore, at any given moment, both ants are the same distance from the anthill.