Answer:
The answer to your question is 13.2 ft
Step-by-step explanation:
Data
length of the ladder = hypotenuse = 16 ft
adjacent side = 9 ft
opposite side = ?
Process
1.- To solve this problem use the Pythagorean theorem
        c² = a² + b²
Solve for b²
         b² = c² - a²
2.- Substitution
         b² = 16² - 9²
3.- Simplification
         b² = 256 - 81
         b² = 175
         b = 13.2 ft
4.- Conclusion
The ladder is  13.2 ft resting against the building.        Â