[tex]3x + x - 4 + 100 = 180[/tex]
[tex]4x + 96 = 180[/tex]
[tex]4x = 180 - 96[/tex]
[tex]4x = 84[/tex]
[tex] \frac{4x}{4} = \frac{84}{4} [/tex]
[tex]x = 21[/tex]
