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:
![\begin{gathered} (4x-12)+120=180 \\ 4x-12=180-120=60 \\ 4x=60+12 \\ 4x=72 \\ x=(72)/(4) \\ x=18 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/9vqn8i2t3n0fn3zrt4hotaz6n3afhpyrnf.png)
The value of x is 18 degrees.