This question has been asked an innumerable amount of times on this forum, so I will just redirect you to pages where a user has already answered this:
1. https://web2.0calc.com/questions/6-2-2-1#r2
2. https://web2.0calc.com/questions/6-2-2-1-1-or-9
3. https://web2.0calc.com/questions/6-2-1-2_5
I figure that these resources are sufficient for you!