It's not C. Use the Geometric Mean for right triangles to solve. In our formula, our values will fit in like this: [tex] \frac{9}{x}=\frac{x}{9+7} [/tex]. Simplifying we have [tex] \frac{9}{x}=\frac{x}{16} [/tex]. Cross-multiply to get [tex] x^2=144 [/tex]. That means that x = 12. First choice above.
