Given: ABCD is a trapezium. ⇒BC∥AD
⇒∠ADC+∠DCB=180∘ (Interior angles on the same side of transversal DC)
⇒120∘+∠DCB=180∘
⇒∠DCB=180∘−120∘
⇒∠DCB=60∘
In a trapezium ABCD side BC is parallel to AD.If ∠ADC=100∘, then ∠DCB=___ ∘