Let's find the height of the triangle. Whatever the height is, when we double it, it'll be x. We need to use the pythagorean theorem.
12²+(x/2)²=18²
144+(x/2)²=324
(x/2)²=180
x/2=13.4164079
x=26.833
X≈26.8
So, the answer is the first option, 26.8.
