1. **Problem statement:** Xavier thinks of a number. He multiplies it by 2 then adds 8. The answer is 20. What number did Xavier think of? 2. **Write the equation:** Let the number be $x$. The operation described is: multiply by 2, then add 8. This gives the equation: $$2x + 8 = 20$$ 3. **Solve the equation:** Subtract 8 from both sides: $$2x + 8 - 8 = 20 - 8$$ $$2x = 12$$ Divide both sides by 2: $$x = \frac{12}{2} = 6$$ 4. **Interpretation:** The number Xavier thought of is $6$. This equation is straightforward and correctly represents the problem.