Answer:
![\text{C. }7.2](https://img.qammunity.org/2022/formulas/mathematics/high-school/hx6ccacr9jjld78rtliglalro2o33ci05g.png)
Explanation:
In the figure, all three triangles are similar. By definition, the corresponding sides of similar polygons must be in a constant proportion. Therefore, we can set up the following proportion to solve for
by dividing corresponding sides:
![(x)/(12)=(12)/(20),\\20x=144,\\x=(144)/(20)=\boxed{\text{C. }7.2}](https://img.qammunity.org/2022/formulas/mathematics/high-school/cmivbqj8ueazlaulmz3a1yryih5465gq56.png)