Concept:The interior angle at D is equal to the given exterior angle by vertically opposite angles, and the sum of interior angles of a quadrilateral is 360∘.Explanation:Given: ∠EDF=70∘.By vertically opposite angles, ∠ADC=∠EDF=70∘.In quadrilateral ABCD, the interior angles are:∠ABC=90∘, ∠BCD=90∘, ∠ADC=70∘, and ∠BAD=t.Sum of interior angles of a quadrilateral is 360∘.So, t+90∘+90∘+70∘=360∘.t+250∘=360∘t=360∘−250∘t=110∘Answer:t=110∘
