Answer
The third angle measures $54.5^{\circ}$.
Work Step by Step
We know that the three interior angles of a triangle equal $180$. If we are already given two of the angles, we can figure out the third angle.
Let us set up the equation to add the three angles together. One angle measures $54.5$, and the other measures $71$. Let $x$ be the measure of the last angle:
$54.5 + 71 + x = 180$
Let's add the constants together on the left side of the equation to simplify:
$125.5 + x = 180$
To solve for $x$, subtract $125.5$ from each side of the equation:
$125.5 - 125.5 + x = 180 - 125.5$
Subtract to simplify:
$x = 54.5$
The third angle measures $54.5$.
