Steps of Construction-

1. Draw an angle of 40° with the help of protractor, naming ∠AOB.

2. Draw a line PQ. Take any point M on PQ.

3. Place the compasses at O and draw an arc to cut the rays of ∠AOB at L and N.

4. Use the same compasses setting to draw an arc O as centre, cutting MQ at X. Set your compasses to length LN with the same radius.

5. Place the compasses at X and draw the arc to cut the arc drawn earlier Y. Join MY.

6. Thus, ∠QMY = 40° and ∠PMY is supplementary of it.