Try finding the scale factor between the two corresponding sides that are given and solve for x.

Another way to solve for x is to create a proportion.
One possible proportion is shown below.

$\frac{24}{9} = \frac{16}{x}$

x = 6 cm

Use the formula for area of a triangle:

$\frac{1}{2}(\text{base})(\text{height})$

What is the scale factor between the larger triangle and the smaller triangle? Find the ratio between corresponding sides.

Scale factor matches proportion.

$\frac{8}{3}$