We can find x by translating the angle with measure 120 degrees from line l1 to its corresponding angle at line l2.
Then, the angle that is supplementary to 120 degrees is inside the triangle and will have a measure of 180-120=60.
Then, we can use the fact that the sum of the measures of the interior angles of a triangle is equal to 180 degrees.
Then, we can find x as:
[tex]\begin{gathered} x+60+90=180 \\ x=180-90-60 \\ x=30\degree \end{gathered}[/tex]
Answer: x = 30º
