1. **Problem statement:** We have a right triangle with vertices C, B, and D, where the right angle is at vertex B. The leg BC adjacent to the right angle is 7 miles long. We need to solve for the hypotenuse CD or any other missing side if more information is given. 2. **Formula used:** In a right triangle, the Pythagorean theorem applies: $$c^2 = a^2 + b^2$$ where $c$ is the hypotenuse, and $a$ and $b$ are the legs. 3. **Important rules:** The hypotenuse is always opposite the right angle and is the longest side. 4. **Intermediate work:** Since only one leg (BC = 7 mi) is given and no other side or angle is provided, we cannot find the hypotenuse or the other leg without additional information. 5. **Conclusion:** To solve the triangle completely, we need either the length of the other leg or the hypotenuse, or an angle measure besides the right angle. **Final answer:** Insufficient information to solve the triangle completely with only one leg length given.