Question: how to find the distance from x-axis?
Answer: Drop perpendicular to the x-axis, it intersects x-axis at the point (1,0,0). The vector from the point (1,0,0) to the point (1,-3, 8) is perpendicular to the x-axis and its length gives you the distance from the point (1,-3,8) to the x-axis. The coordinates of a vector are (0,-3,8).