The angles are co-interior angles, whose sum is equal to 180. So the equation for x is,
[tex]4x-12+120=180[/tex]
Simplify the equation for x.
[tex]\begin{gathered} 4x-12+120=180 \\ 4x=180-120+12 \\ x=\frac{72}{4} \\ =18 \end{gathered}[/tex]
The value of x is 18.
Determine the measure of unknown angle.
[tex]\begin{gathered} 4x-12=4\cdot18-12 \\ =72-12 \\ =60 \end{gathered}[/tex]
The measure of unknown angle is 60 degree.
