1. **Problem:** Find the missing angle $x$ in a quadrilateral with angles $x^\circ$, $78^\circ$, and two right angles ($90^\circ$ each). 2. **Formula:** The sum of interior angles in any quadrilateral is $$360^\circ$$. 3. **Step 1:** Write the equation for the sum of angles: $$x + 78 + 90 + 90 = 360$$ 4. **Step 2:** Simplify the known angles: $$x + 78 + \cancel{90} + \cancel{90} = 360$$ $$x + 168 = 360$$ 5. **Step 3:** Solve for $x$ by subtracting 168 from both sides: $$x + 168 - 168 = 360 - 168$$ $$x = 192$$ 6. **Answer:** The missing angle $x$ is $192^\circ$. This completes the solution for the first problem.