Concept: In a rhombus, diagonals bisect the interior angles, and adjacent angles are supplementary.Explanation:In rhombus PQRS, diagonal QS bisects ∠PSR.Given ∠PSQ=35∘, so ∠PSR=2×35∘=70∘.Adjacent angles in a rhombus are supplementary.Thus, ∠SRQ=180∘−70∘=110∘.Diagonal PR bisects ∠SRQ.So, ∠PRQ=21×110∘=55∘.