Answer:
<em>x=21°</em>
Step-by-step explanation:
<u>Relations Between Angles</u>
We need to recall two basic relations:
* Two angles opposite by crossing lines are always equal.
* The sum of angles in a triangle is 180°
We'll add some variables to the image, so x is easier found. Please check the image below.
The angles U and 54° are opposite and they must be equal, thus U=54°
Since m and n are parallel and they are crossed by a line, the angles V and U are equal, thus V=54°
Finally, The sum of the angles inside the triangle RST must be equal to 180°:
2x+4x+54=180
Joining like terms:
6x=180-54=126
Solving:
x=126/6
x=21°