Answer:
The answer is 405
Step-by-step explanation:
As you can see, this triangle has a base, a perpendicular and a hypotenuse, So using the formula H^2= P^2+B^2, we can see that it has base 18, perpendicular 9 and hypotenuse AB, Therefore, 18^2+9^2= AB^2...324+81=405!
