Let us try to draw the quadrilateral:
Step 1: Draw BC = 6 cm.
Step 2: At B, draw an angle = 60∘. Along that angle, make an arc of 5 cm and mark it as point A.
Step 3: From A, draw an arc of 6 cm.
Step 4: From C, draw an arc of 7 cm such that it intersects the arc made from A. Mark the point of intersection as D.
Step 5: Join ABCD to complete the quadrilateral.
Is this quadrilateral unique?
Yes it is.
If we move it, keeping all the angle length constant △ ABC will change. So, there is only one quadrilateral ABCD with AB = 5 cm, BC = 6 cm, CD = 7 cm, BA = 6 cm, ∠ ABC= 60∘.