The prove, segment r is perpendicular to segment r. is achieved using transitive property and definition of perpendicular lines
How to complete the proof
The two column proof is written as follows
Statement Reason
q || r given
q ⊥ s given
∠ 3 = 90 deg definition of perpendicular lines
∠ 3 ≅ ∠ 2 corresponding angles are equal
∠ 2 = 90 deg transitive property
r ⊥ s definition of perpendicular lines