First of all remeber that "a number" means we don't know the number or it could be many but not all numbers, so it is represented by x.
5. 1/2x + 6 > 20
6. 12 + 3x < -11 (They asked for the opposite of 11, the opposite of a positive number is always the negative of that number, and the opposite of a negative number is the positive of that number).
7. 2x - 8 < 5