You already know the sum of the measures of the interior angles of a triangle add up to 180 degrees, so make all the angles add up to 180 in an equation.
(3x + 4) + (x + 8) + (2x) = 180
Combine like terms.
6x + 12 = 180
Subtract 12 from both sides.
6x = 168
Divide both sides by 6.
[tex] \boxed {x = 28} [/tex]
