Answer:
11.6 ft
Step-by-step explanation:
I attached a diagram for you to easily visualize this problem.
To solve this problem, you would use the pythagorean theorem. The 12-ft ladder is the hypotenuse and the 3 ft from the barn is one of the side legs. You want to find the length of the "other side leg", or the height of the barn.
Substitute 3, 12, and x into the pythagorean theorem like so.
a^2 + b^2 = c^2
3^2 + x^2 = 12^2
Evaluate the exponents.
9 + x^2 = 144
Subtract 9 from both sides.
x^2 = 135
Square root both sides.
x = 11.618
Round this to the nearest tenth: 11.6 feet.