Hello from MrBillDoesMath!
Answer: Â x = 71 degrees. Yes, the ladder meets safety standards
Discussion:
The problem describes a right triangle with hypotenuse 12, the side against the ground is 4, and the angle between those two sides is "x". Â For this triangle,
cosx = (side adjacent to angle) / hypotenuse
    =  4                    / 12
    =  1/3
To find "x" take the inverse cosine of each side to find that :
x  is approximately 70.52 degrees. That's 71 degrees rounded to the nearest degree.
Thank you,
MrB