A B C D is a cyclic quadrilateral. Therefore ∠DCB=180∘−∠A=180∘−60∘=120∘∠ABC=80∘; therefore ∠BCQ=180∘−120∘=60∘ And ∠CBQ=180∘−80∘=100∘ (because, sum of angles on a line =180∘) Then in ΔBCQ,∠Q=180∘−(100∘+60∘)=20(∵ sum of angles of triangle =180∘)