In parallelogram LMNO,
Since line LM || line QN, same side interior angles L and O will be supplementary angles.
i.e, angle L + angle O = 180
=> x+40 + 3x = 180
=> 3x + x + 40 = 180
=> 4x + 40 = 180
=> 4x = 180-40
=> x = 140/4
=> x = 35
now,
angle O = (3x)°
= (3 × 35)°
= 105°
