Answer:
[tex]3x = 12x - 81[/tex](vertically opposite angles)
[tex]→3x - 12x = - 81[/tex]
[tex] →- 9x = - 81[/tex]
[tex]→x = \frac{ - 81}{ - 9} [/tex]
[tex]→x = \frac{81}{9} [/tex]
[tex]→x = 9[/tex]
hope it helped you:)
