8. There is no solution. The absolute value of a number is always positive.
9. There are two solutions. Since the absolute value of a number is always positive, a solution can either be 4 or -4.
10. There is no solution because of the same reason for number 8.
11. There is one solution. There really is not -0.
12. There are two solutions. Since the absolute value is always positive, the solution can be either 15 or -15.
