Warning, don’t look at these if you still want to try to solve the riddles.
#1: Flip on two switches and leave them on for a bit. Flip one off. Go up to the room. If the light is on, you know which switch it is. If the light is off and warm, it’s the switch that you just flipped off. If it’s off and cool, it’s the one that you never touched. Voila! – This one I could NOT get on my own. I do not feel dumb at all, hardly anyone at my work could get it- but now, if I am ever in that situation, I will know just what to do.
#2: The friend is Sally.
#3: Roman numerals. XIX, take “one” away and you get XX.