The given details are AB = BC = 6 cm, AD = DC = 4.5 cm and ∠B = 120°.
Steps to construct a quadrilateral:
Step 1- Draw a line AB = 6cm
Step 2- Construct and angle of 120o at B.
Step 3- Cut an arc of radius 6cm with B as the center to mark that point as C.
Here, AC is about 10.3cm in length which is greater than AD + CD = 4.5+4.5=9cm
We know that sum of the two sides of a triangle is always greater than the third side.
AD + CD < AC
∴ Construction is not possible.