We can see that the angle (4x-12) and 120 are supplementary. That is, they add 180 degrees.
We can conclude that because the supplementary angle for (4x-12) is similar to the angle of 120 degrees.
Then, we can work from this equality:
[tex]\begin{gathered} (4x-12)+120=180 \\ 4x-12=180-120=60 \\ 4x=60+12 \\ 4x=72 \\ x=\frac{72}{4} \\ x=18 \end{gathered}[/tex]The value of x is 18 degrees.
