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∘