Answer
$$ 71 ^{\circ}$$
Work Step by Step
We know that angle ABC is the sum of the measures of angle 1 and angle 2. Thus, it follows:
$$ m\angle ABC = m \angle 1 + m \angle 2 \\ m \angle ABC = 42 ^{\circ} + 29 ^{\circ} \\ m \angle ABC = 71 ^{\circ}$$
