For this the easiest way is to picture the situation. You will notice that you have right triangle in front of you. Length of ladder is you largest side of triangle. Right angle is oposite from it. That means we can use simple trigonometric functions.
Because of the angle we need it is easiest to use cosine function
cos(x) = [tex] \frac{side-that-is-next-to-that-angle}{hypotenuse} [/tex]
cos(x) = 4/7
x = arccos(4/7) = 55.15 degrees
Answer is C
