Answer:
1. Set the compass width over half length of segment FG
2. place the compass fix end at F and draw 2 arcs above below FG
3. without change the compass width, place the fix end to G
4. draw 2 arcs above and below FG to intersect with the previous arcs at M and N
5. Use straightedge draw a line pass through M and N, the perpendicular bisector is done
Explanation: