Skill: Apply the triangle angle-sum relationship

The three interior angles of every triangle add up to $180^\circ$:

$$\text{Angle 1}+\text{Angle 2}+\text{Angle 3}=180^\circ$$

To find a missing angle, add the known angles and subtract that sum from $180^\circ$.

Example: A triangle has angles measuring $52^\circ$, $67^\circ$, and $x^\circ$. Find $x$.

1. Write the angle-sum equation:

$$52+67+x=180$$

2. Add the known angles:

$$119+x=180$$

3. Subtract $119$ from both sides:

$$x=61$$

The missing angle is:

$$\boxed{61^\circ}$$

Check: $52^\circ+67^\circ+61^\circ=180^\circ$, so the answer is correct.