Question

the diagram shows a triangle.
what is the value of c?
c = \square°

Explanation:

Step1: Sum angles to 180°

$30 + (6c - 3) + (3c - 18) = 180$

Step2: Simplify left side

$30 - 3 - 18 + 6c + 3c = 180$
$9 + 9c = 180$

Step3: Isolate term with c

$9c = 180 - 9$
$9c = 171$

Step4: Solve for c

$c = \frac{171}{9}$

Answer:

$19$