408.

From Thread 1

Well Done!

You see, just plus one on 199 and 209! You'll end up with 200 and 210. Thats 410. Remember you added 2! So just minus that, and you'll get 408! Of course you cheated.

(But if you didn't, well done!)

Now.

900 + 100 = ?

• 1000.
• 100!