
This means that the line of symmetry is line I.

This means that the line of symmetry is line m.
1.

This matches with Q.
In this number, the line of symmetry is I. If you reflect T across line I, you will get point Q. This is because they are right across from each other with line I between them, and they are both the same distance from line I.
2.

This matches with S.
Point S lies on the line of symmetry; thus, S reflects itself.
3.

This is similar to number 1. If you reflect Z across line I, you will get point X because they are directly across each other with line I between them and they have the same distance from the line of symmetry.
4.

This time, S isn't on the line of symmetry. The line of symmetry is the vertical line m. Point Y matches with point S because they are directly across each other with line m between them. They are also the same distance apart from line m.
5.

This is very similar to number 1. This matches with F. The point directly across the line of symmetry is F.
6.

This is the exact same as number 5! With the same line of symmetry, B matched with F. Thus, F must match with B!
Here are the matches:
3-X
5-F
6-B
4-Y
1-Q
2-S