Answer:
45
Step-by-step explanation:
We are seen with two lines crossing each other and the angle in which a line has is 180 degrees. Also, the angles labeled 3x and x are supplementary angles, which mean they add up to 180 degrees. Using this information, we can set up an equation.
[tex]x+3x=180[/tex]
[tex]4x=180[/tex]
[tex]x=45[/tex]
