1. **State the problem:** Find the perimeter of rectangle PQRS with vertices P(4,1), Q(4,7), R(8,7), and S(8,1). 2. **Recall the formula for perimeter of a rectangle:** $$\text{Perimeter} = 2(\text{length} + \text{width})$$ 3. **Calculate the length and width:** - Length PQ (vertical side) is the difference in y-coordinates: $$|7 - 1| = 6$$ units. - Width PS (horizontal side) is the difference in x-coordinates: $$|8 - 4| = 4$$ units. 4. **Calculate the perimeter:** $$\text{Perimeter} = 2(6 + 4) = 2 \times 10 = 20$$ units. 5. **Answer:** The perimeter of rectangle PQRS is **20 units**.