ANSWER:
[tex] \large\color{orange}{ \tt{3x+30+90=180}}[/tex]
[tex] \large\color{orange}{ \tt{3x+120=180}}[/tex]
[tex] \large\color{orange}{ \tt{3x=180−120}}[/tex]
[tex] \large\color{orange}{ \tt{3x=60}}[/tex]
[tex] \large\color{orange}{ \tt{x=60/3}}[/tex]
[tex] \large\color{orange}{ \tt{x = 20}}[/tex]
Hope It's Help