Since the angles are supplementary, their sum must add up to 180 degrees.
[tex] (6x + 8) + (12x-8) = 180 [/tex]
[tex] 18x = 180 [/tex]
[tex] x = 10 [/tex]
Now that we know x = 10, we put it for each angle to find the measure of the angles.
[tex] 6 * 10 + 8 = 60 + 8 = 68 [/tex]
[tex] 12 * 10 -8 = 120 - 8 = 112 [/tex]
So, m∠ABC = 68° and m ∠DEF = 112°
