Final answer:
The first number in an ordered pair of numbers that corresponds to a point on a coordinate system is the x-coordinate, which indicates the horizontal position of the point on a Cartesian plane.
Step-by-step explanation:
The first number in an ordered pair of numbers that corresponds to a point on a coordinate system is the x-coordinate. In the context of a rectangular (Cartesian) xy-coordinate system, points are located using two coordinates. The first, the x-coordinate, specifies the horizontal position, indicating how far to the left or right the point is from the vertical y-axis. The second, the y-coordinate, specifies the vertical position, indicating how far up or down the point is from the horizontal x-axis. When plotting the point (x, y) on a Cartesian plane, you would move x units along the horizontal axis and then y units along the vertical axis.
For a three-dimensional coordinate system, the concept extends by adding a third coordinate, the z-coordinate, which specifies the depth, indicating how far in or out of the page the point is located. The ordered triple (x, y, z) represents the location in three-dimensional space. Another system, polar coordinates, uses a different approach by specifying the distance from the origin to the point, and the angle from the positive x-axis to reach that point.