Common sense

Those were the worst problems. I would be instantly filled with encompassing and irrational rage when I saw one of those and just knew I would have to guess and check my way to Hell and back to even leave an answer in the box.

Easy, 1+1 = 3. 1 thing and a nother thing can make another thing making it that three things are now there e.g. parents.

Could be that it's in base 2 in which case 1+1=10 Or that's it's the boolean + in which case 1+1=1.