You have to use the Geometric Mean for triangles to find x. Our form will look like this:

which simplifies to

. Cross multiply to get

. Therfore, x = 4. Usually when we take the square root of a number we will end up with both the principle (positive) root and the negative one as well. But since the 2 things in math that will never EVER be negative are time and distance/length, we will not consider the -4. x = 4