Explanation:
Given that point Y is on line segment XZ, and YZ = 4 and XY = 2, you can use the segment addition postulate to find the length of XZ.
Segment Addition Postulate: If three points A, B, and C are collinear and B is between A and C, then AB + BC = AC.
In this case, point Y is between points X and Z, so we have:
XY + YZ = XZ
2 + 4 = XZ
6 = XZ
Therefore, the length of XZ is 6 units.