Answer:
21.6 in
Explanation:
since it's a right triangle, use the pythagorean theorem (a^2 + b^2 = c^2)
12^2 + 18^2 = c^2
144 + 324 = c^2
468 = c^2
c = square root of 468
c = 21.6333 (...) in
since you have to round it up to the nearest tenth, then the answer should be 21.6 in