Question

what is the value of c? 4c+9° c+42° 30° c = □°

Explanation:

Step1: Use exterior angle theorem

The exterior angle of a triangle is equal to the sum of the two non - adjacent interior angles. So, we have the equation $4c + 9=(c + 42)+30$.

Step2: Simplify the right - hand side

Simplify $(c + 42)+30$ to get $c+72$. So the equation becomes $4c + 9=c + 72$.

Step3: Subtract c from both sides

Subtract $c$ from each side: $4c - c+9=c - c + 72$, which simplifies to $3c+9 = 72$.

Step4: Subtract 9 from both sides

Subtract 9 from each side: $3c+9 - 9=72 - 9$, so $3c=63$.

Step5: Divide both sides by 3

Divide both sides by 3: $\frac{3c}{3}=\frac{63}{3}$, which gives $c = 21$.

Answer:

$21$