To draw ∆PQR with the given conditions, follow these steps:

1. Draw a line segment QR of length 4.5 cm.
2. At point Q, draw an angle of 80° using a protractor. Label the vertex of the angle as Q.
3. At point R, draw an angle of 55° using a protractor. Label the vertex of the angle as R.
4. Connect points Q and R to form the triangle PQR.

To draw the perpendicular bisector of side QR, follow these steps:

1. Find the midpoint of QR by measuring the length of QR and marking the halfway point. Label this point as M.
2. Using a compass, place the needle on point M and draw an arc that intersects QR on both sides. Label these points as A and B.
3. Adjust the compass to a length greater than half of QR and place the needle on point A. Draw an arc above QR.
4. Without changing the compass width, place the needle on point B and draw an arc above QR that intersects the previous arc.
5. Connect the intersection points of the arcs above QR to form a line. This line is the perpendicular bisector of QR.