Answer
$x=40$
Work Step by Step
The sum of the four interior angles of a quadrilateral is $360^\circ$.
Thus, the equation needed to find the value of. $x$ is:
$\begin{align*}
x^\circ+100^\circ+120^\circ+100^\circ&=360^\circ\\
x^\circ+320^\circ&=360^\circ\end{align*}$
Solve the equation by subtracting $320^\circ$ from each side:
$\begin{align*}
x^\circ+320^\circ-320^\circ&=360^\circ-320^\circ\\
x^\circ&=40^\circ\\
x&=40
\end{align*}$
The angle is acute and the value of $x$ is $40$ so the answer is reasonable.
