Concept:Opposite angles in a parallelogram are equal.Explanation:In a parallelogram PQRS, the opposite angles are equal. This means that angle P is equal to angle R, and angle Q is equal to angle S.So, we have $∠P = ∠R$.We are asked to find the value of $∠P - ∠R$.Since $∠P = ∠R$, we can substitute $∠P$ with $∠R$ (or vice versa) in the expression.Therefore, $∠P - ∠R = ∠P - ∠P = 0°$.Alternatively, $∠P - ∠R = ∠R - ∠R = 0°$.Answer:0°