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

Read also:

• Scientists Are Getting Closer to Finding Evidence of the Fifth Force - Yahoo
• Brain cortex structure linked to mental abilities and psychiatric disorders - Medical Xpress
• What did your sister do to you that you can never forget?
• What is the most ridiculous obviously false verse in the Bible?
• Do they have internet in hell? Most people on here seem like damned souls or demons.
• Sarepta reports second patient death after treatment with Duchenne gene therapy - statnews.com
• Who was the most ignorant American you have ever met?
• Why do most people care so much about what others think? Are they afraid of society norms?
• Heart in distress? 9 silent symptoms you shouldn’t overlook - Times of India
• China's electric cars are cheaper, but is there a deeper cost? - BBC