1. Problem: Find the missing angle $x$ in a triangle with angles 55°, 50°, and $x$°. 2. Formula: The sum of angles in a triangle is always 180°. 3. Calculation: $$x + 55 + 50 = 180$$ $$x + 105 = 180$$ $$x = 180 - 105$$ $$x = 75$$ 4. Explanation: Since the sum of all angles in a triangle must be 180°, subtract the sum of the known angles from 180° to find $x$. This is the first problem solved step-by-step as requested.