Absolute value of a number is its non-negative value.

• |-a| = a; a > 0;
  
• |a| = a; a > 0;
  
• |0| = 0;
  

• |-4| = 4; Absolute value of -4 is 4
  
• |-3.2| = 3.2; Absolute value of -3.2 is 3.2
  
• |20| = 20; Absolute value of 20 is 20