Answer:
17
Step-by-step explanation:
First of all, based on the Pythagorean theorem, a^2 + b^2 = c^2
(it's very important that the ∠ABD angle is 90 degrees)
8^2 + 15^2 = s and 5^2 + 15^2 = CD (but the original question doesn't want the value of CD, so we just need to solve for s)
64 + 225 = 289 now remember, 289 is s^2, and we only want the value of s, so we have to find its square root: √289 = 17
Hope it helped!
