Answer: r = 16
Step-by-step explanation:
We know that triangle ABC is a right triangle.
Therefore, we can use the pythagorean theorem to solve for r.
r^2 + 30^2 = (r+18)^2
r^2 + 900 = r^2 + 36r + 324
Combine like terms:
36r = 576
Divide both sides by 36:
r = 16
