Question 1195383
I assume that the guy wire is a straight line. 
<pre>

First, we can visualize a diagram. We can imagine the guy wire of a right angles triangle. The hypotenuse is 20', and the adjacent side is 8'.

We only need to find the opposite side. We can do that by using the Pythagorean Theorem.

{{{8^2+x^2=20^2}}}
x is approximately 18.33.

now we add 18.33' with 12' to get:
30.33'

</pre>
Solved.