1. **Stating the problem:** We have a square with four right angles (each 90°). Inside the square, there are angles 40°, 80°, and an unknown angle $x$°. 2. **Understanding the problem:** Since the figure is a square, each corner is 90°. The angles inside the square relate to these corners and possibly to each other. 3. **Key fact:** The sum of angles around a point or along a straight line is 180° or 360°, depending on the context. 4. **Using the square's properties:** The sum of angles in any triangle is 180°. If the angles 40°, 80°, and $x$° are part of a triangle inside the square, then: $$40° + 80° + x° = 180°$$ 5. **Solving for $x$:** $$x = 180° - 40° - 80°$$ $$x = 60°$$ 6. **Conclusion:** The unknown angle $x$ is 60°.