If you double a number and add 5 to the result, then that's 20 more than half of the original number. What's the original number? Let's be accurate as possible.
Let x be the original number. 2 * x + 5 = 20 + x / 2. 2 * x - x / 2 = 15. 4 * x - x = 30. 3 * x = 30. x = 10.
The answer: 4.