(b) 7
The distance of a point from the x-axis is its y-coordinate (ordinate). For the point (−1, 7), the y-coordinate is 7.
Source: Chapter 7, Section 7.1
The key definition from Section 7.1: "The distance of a point from the x-axis is called its y-coordinate, or ordinate." The x-coordinate (−1) gives the distance from the y-axis, not the x-axis. Distance is always non-negative, so even if the ordinate were negative, we'd take its absolute value — but here it is already positive (7).