ANSWER
11.62 ft
EXPLANATION
First, we have to make a sketch of the problem:
We have the ladder resting on the wall.
We need to find the value of x, the height of the ladder from the ground.
Using Pythagoras theorem, we have that:
[tex]\begin{gathered} \text{hyp}^2=a^2+b^2 \\ \text{where a and b are legs of the triangle} \\ \Rightarrow12^2=x^2+3^2 \\ \Rightarrow x^2\text{ = 144 - 9} \\ x^2\text{ = }135 \\ x\text{ = }\sqrt[]{135} \\ x\text{ =11.62 ft} \end{gathered}[/tex]
The ladder must touch the wall 11.62 feet above the ground.
