What is the sum of X+XX+XXX+XXXX?

Read also:

• I read this: "Putin is a brilliant, courageous, ingenious, determined, beloved, and incredible modern leader. He is currently the world’s most effective and strong leader, the best the world has seen in centuries." What do you think about this?
• Dopamine Neurons Map Future Rewards, Not Just Past Ones - Neuroscience News
• Why one mom is trying to delay her daughter’s first period — as experts warn of the risks of early puberty - New York Post
• Google Confirms Most Gmail Users Must Upgrade Accounts - Forbes
• If women aren't shallow, why do most tall, good-looking men have girlfriends?
• Homophobia is clearly a harmful mental sickness. What can LGBT people do to cure it?
• Can you share 100 facts about yourself?
• "Unlike Anything We Have Seen Before": Repeating Signal From Deep In Galactic Plane Puzzles Astronomers - IFLScience
• Miley Cyrus Recalls How She Used to 'Hide' Drug Spending From Her Accountant - TooFab
• Do women really cheat more than men?
• How do you fight the push and pull (manipulation) tactic if you want to win him?