Question

1. if (mangle9 = 110^{circ}), then (mangle8=)? a. (70^{circ}) b. (80^{circ}) c. (100^{circ}) d. (108^{circ})

Explanation:

Step1: Identify angle - relationship

$\angle9$ and $\angle8$ are supplementary angles (linear - pair).

Step2: Use the supplementary - angle formula

The sum of two supplementary angles is $180^{\circ}$. Let $m\angle9 = 110^{\circ}$ and $m\angle8=x$. Then $m\angle9 + m\angle8=180^{\circ}$, so $x = 180^{\circ}-m\angle9$.

Step3: Calculate the measure of $\angle8$

Substitute $m\angle9 = 110^{\circ}$ into the formula: $m\angle8=180^{\circ}-110^{\circ}=70^{\circ}$.

Answer:

A. $70^{\circ}$