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

Read also:

• What is the best/cute/funny/playful chat/conversation between brother and sister?
• What do you think about wearing sheer pantyhose?
• The world of the Harry Potter series is usually considered bad worldbuilding. What are some examples of actually good worldbuilding in the books/movies?
• Why is (n-1)(n+1)=n^2-1?
• What are some of the best photos of your favorite Korean model?
• Why did Donald Trump and Melania Trump sleep in different rooms?
• As it happened: Breakaway holds on for victory ahead of GC contenders on the final stage of the Critérium du Dauphiné - Cyclingnews
• Which unexpected celebrity has done a bold or revealing photoshoot?
• Is it still wrong to spread misinformation even if it's only to troll people rather than harming them?
• Why are the Chinese so sensitive to Western criticism?
• Have you ever accidentally seen your mother-in-law doing something that was private to her?
• I like this guy and his personality is AMAZING. He’s everything I want EXCEPT I’m not 100% attracted to him. I’ve dated some really hot guys and I’m wondering if that’s ruined dating for me? What do I do?