Option C: 8 units
The distance of a point from the x-axis is its y-coordinate (ordinate). For the point (−6, 8), the ordinate is 8, so the distance from the x-axis is 8 units.
The textbook (Section 7.1) clearly states: "The distance of a point from the x-axis is called its y-coordinate, or ordinate." Since distance is always non-negative, we take the absolute value of the y-coordinate. Here, |8| = 8 units. The x-coordinate (−6) gives distance from the y-axis, not the x-axis — a common confusion to avoid.