The angle of a straight line is 180° so you can add both angle sides and equate it to 180° (6x - 10) + (6x + 10) = 180 join like terms 6x + 6x -10 + 10 = 180 12x = 180 (-10 and +10 cancels out) [tex] \frac{12x}{12} = \frac{180}{12} [/tex] (12 and 12 cancels out) x = 15 Your answer will the the first option a) x = 15
