#### Answer

$A=30\text{ cm}^2$

#### Work Step by Step

To find the area of a trapezoid, we use the formula $A=0.5(b_1+b_2)h$, where $b_1$ and $b_2$ are the respective bases and $h$ is the height.
We plug in the values, as shown in the diagram, to get:
$$A=0.5(b_1+b_2)h
\\A=0.5(9\text{ cm}+6\text{ cm})4\text{ cm}
\\A=0.5(15\text{ cm})(4\text{ cm})
\\A=30\text{ cm}^2$$