1. The definition of the absolute value function is y = x if x is nonnegative, and y = -x if x is negative. So in order to evaluate , you put in the value for x, and then if , the value stays unchanged; otherwise, it becomes positive. For example, if x = 0, then , so . If x = -3, then , and .
2. After you evaluate , you see that . I'm not sure what you are asking here, though.