I did the birthday cake candles.
What I did for it was I put 1-11 in a line in order. First the candles went up to over than a year, i tallied them up on how much they would need. Like:
1 i 2 years
2 i+1=2
3 ii-i=1+ii=3
His first birthday he only needed one so there was one tally, the second birthday (because the first candle was still in use) i only needed one more so i added one more to make two. His third birthday Ben needed to take- way one because his first candle from his first birthday would run out so Ben only had one candle left from his second birthday so - to make 3 he needed to buy two more. then you keep going like that. When you've gone up to 11 you added all of them up (not including all of the candles that ran out because you would of already counted them . You should get 36.