CPM Homework Help : PC Problem 4-116

Find the length of $x$ in the triangle below.
Right triangle, horizontal hypotenuse, segment from right angle perpendicular to hypotenuse, divides hypotenuse into 2 sections, left section labeled 3, right section labeled 15.

Hint:

These are similar triangles. Set up a proportion and solve for $x$ .

Proportion:

$\frac{3}{x}=\frac{x}{15}$