Steps of construction:
(a) Draw an angle of 40 degree with the help of protractor, naming ∠ AOB.
(b) Draw a line PQ.
(c) Take any point M on PQ.
(d) Place the compasses at O and draw an arc to cut the rays of ∠AOB at L and N.
(e) Use the same compasses setting to draw an arc O as centre, cutting MQ at X.
(f) Set your compasses to length LN with the same radius.
(g) Place the compasses at X and draw the arc to cut the arc drawn earlier Y.
(h) Join MY.
(i) Thus, < QMY = 40 degre and < PMY is supplementary of it.
