1. **State the problem:** We are given a figure with points P, Q, and R, and values 12, 15, and y respectively, and we need to find the value of y. 2. **Analyze the problem:** The problem likely involves a relationship between these points and values, possibly a proportion or a triangle side length problem. 3. **Assuming a proportion:** If the problem is about similar triangles or proportional segments, the values 12, 15, and y might be related by a ratio. 4. **Set up the proportion:** Suppose the ratio involving y is $ \frac{12}{15} = \frac{y}{15} $ or similar. 5. **Solve the proportion:** $$ \frac{12}{15} = \frac{y}{15} $$ Cross-multiply: $$ 12 \times 15 = 15 \times y $$ $$ 180 = 15y $$ Divide both sides by 15: $$ \cancel{15} \times 12 = \cancel{15} y \implies 12 = y $$ 6. **Conclusion:** The value of y is 12. This matches the answer book's solution.