Answer
$13\ ft$
Work Step by Step
Step 1. Draw a diagram as shown in the figure, where $x$ is the length of the wire. The height of the tree is 1 foot shorter than the wire, or $x-1$.
Step 2. Using the Pythagorean's Theorem in the right triangle, we have $(x-1)^2+5^2=x^2$ or $x^2-2x+1+25=x^2$ which gives $2x=26$
Step 3. The solution is $x=13\ ft$
