Answer:
x = 25°
Step-by-step explanation:
There are different ways to get there.
<h3>1.</h3>
The unmarked angle at bottom left is an alternate interior angle with the one at the top marked 50°. So, it is congruent to 50°.
That makes the angles along the line at the bottom be ...
50° +x° +105° = 180° . . . . . the measure of a linear angle
x° = 180° -155° = 25°
__
<h3>2.</h3>
The unmarked angle at top right is a same-side interior angle relative to the one at bottom marked 105°. As such it is supplementary to 105°, and has measure ...
180° -105° = 75°
This angle (upper right) is an exterior angle to the triangle. As such, it is equal to the sum of the two "remote" interior angles of the triangle—the ones marked 50° and x°.
75° = 50° +x°
25° = x° . . . . . . . subtract 50°
__
<h3>3. </h3>
The unmarked interior angle of the triangle is an alternate interior angle with the one marked 105°. So, it is congruent to 105°. The sum of the triangle interior angles is 180°, so you have ...
x° +50° +105° = 180°
x = 180° -155° = 25° . . . . as we had with our first approach
. This yields 
