Question

in the figure, a || b. what is the value of x?
$(3x + 9)^{circ}$
$129^{circ}$

Explanation:

Step1: Identify supplementary angle

$\angle 6 = 180^\circ - 129^\circ = 51^\circ$

Step2: Set equal to corresponding angle

$3x + 9 = 51$

Step3: Solve for x

$3x = 51 - 9 = 42$
$x = \frac{42}{3} = 14$

Answer:

$14$