The correct option is
B 80∘ From the figure,
∠ADE+∠ADC=180∘ [Linear pair]
⇒100∘+∠ADC=180[∵∠ADE=100∘] ⇒∠ADC=180∘−100∘=80∘ In quadrilateral ABCD
∠ADC+∠DAB+∠ABC+∠BCD=360∘ ∴ [Sum of all angles of quadrilateral is
360∘]
⇒80∘+60∘+∠ABC+120∘=360∘ ⇒∠ABC+260∘=360∘⇒∠ABC=100∘ But,
∠ABC+x=180∘ [Linear pair]
∴100∘+x=180∘ Hence,
x=80∘