Use the Geometric Mean Theorem and your knowledge of proportions to find the value of x.

Answer:
[tex]x=9.6cm[/tex]
Step-by-step explanation:
[tex]x=\frac{2Area}{20}\\\\Area = \frac{16 * 12}{2} = 96 cm^{2}\\ \\x = \frac{2 * 96}{20} = \frac{192}{20} = \frac{48}{5} = 9.6 cm[/tex]