How do I solve this problem on absolute values?

Question

A. Find a value of a for which |-a| does not equal a

 

B. For what values of a does |-a|=a hold true?

Answer 1

|-a| does not equal a when a < 0; that is, when a is a negative number.  For example, choose a = -3:

 

|-a| = |-(-3)| = |3| = 3, but a = -3, so |-a| ≠ a