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

Read also:

• Have you ever had a bad gut feeling about someone and it was right?
• Exploring the cosmos fills us with wonder, Pope tells scientists - Vatican News
• Which type of physical cable has fastest transmission speed?
• Why would my nipples hurt when I touch them?
• What is a good way to conduct an interview?
• How is sex with a woman for gay men?
• Does having the wrong address on my car insurance invalidate my policy?
• Why do liberals think it is okay to steal votes while the rest of us obey the law(s)?
• Newspaper headlines: 'A generation let down' and 'Israel claims control' - BBC
• Have you ever witnessed political correctness harm someone?