#### Answer

$\angle x=25^{\circ}$

#### Work Step by Step

We can see, that the sum of the two angles ($20^{\circ}$ and $\angle x$) is $45^{\circ}$.
We can write the following equation:
$20^{\circ}+\angle x=45^{\circ}$
$\angle x=45^{\circ}-20^{\circ}$
$\angle x=25^{\circ}$