Question

1. find the measure of ∠abc. m∠abc =

Explanation:

Step1: Identify angle - addition principle

The measure of $\angle ABC$ is the sum of $\angle ABD$ and $\angle DBC$.

Step2: Add the given angles

$m\angle ABC=m\angle ABD + m\angle DBC$. Given $m\angle ABD = 40^{\circ}$ and $m\angle DBC=30^{\circ}$, so $m\angle ABC=40^{\circ}+30^{\circ}$.

Answer:

$70$