Question

what is the value of r?

Explanation:

Step1: Identify angle - relationship

The larger angle of $80^{\circ}$ is composed of the smaller angle $r$ and the $51^{\circ}$ angle. So, $r + 51^{\circ}=80^{\circ}$.

Step2: Solve for $r$

Subtract $51^{\circ}$ from both sides of the equation: $r=80^{\circ}- 51^{\circ}$.

Answer:

$29^{\circ}$