The correct option is
C 30∘
Given:
∠BAD=120∘ and ∠DBC=x
∠B=2∠DBC=2x [Since, diagonals bisect the angles in rhombus]
We have,
∠DAB+∠ABC=180∘ [Co-interior angles on the same side of transversal]
⇒120∘+2x=180∘
⇒2x=180∘−120∘
⇒x=602=30∘
Hence, the value of
x is
30∘ .