Please help with geometry!

28 ft
First, let's find the tower height.
[tex]\frac{3}{8} = \frac{10}{a} \\=> 3a = 80\\=> a = 80/3[/tex]
Second, let's find the length of the guy wire with the Pythagoras theorem.
[tex]c = \sqrt{a^{2} + b^{2} } \\c = \sqrt{10^{2} + (80/3)^{2}}\\c = \sqrt{100 + 711.11}\\c = \sqrt{811.11} \\c = 28.48[/tex]
So in conclusion, the length of the guy wire to the nearest foot is 28 ft