Answer:
4
Step-by-step explanation:
A simple matter of using Pythagoras. The hypotenuse is the ladder, and one of the legs is the wall, and we have to figure out the value of the other leg.
The Pythagorean formuda is (hypotenuse = a): a² + b² = c² (b and c are the other sides)
applying the values: a = 5 and b or c is 3 (I'll put b = 3)
5² = 3² + c²
25 = 9 + c²
25 - 9 = c²
16 = c²
√16 = c
4 = c
c = 4