Answer
$$A=2$$
Work Step by Step
To find the area of the region, we consider the following integral.
So, we get
\begin{align}
A&=\int_{x=1}^{x=2} \int_{y=1}^{y=3} d y d x\\
&=\int_{x=1}^{x=2}[y]_{1}^{3} d x\\
&=\int_{x=1}^{x=2} 2 d x\\
&=[2 x]_{1}^{2}\\
&=2
\end{align}
