Determine whether each statement if always, sometimes, or never true. Explain.
Points X and Y are in plane z. Any point collinear with X and Y is in plane Z.
This is always true. Since points X and Y are in plane Z, the line containing X and Y is in plane Z by postulate 2.5. If the point is collinear with X and Y, then it lies on that line which is containing in plane Z.