Excuse me for my english, but I tried very hard to.=)
A: 379A - New Year Candles
Let cura amount of new candles, curb — amount of burnt out. Initially cura = a, curb = 0, after burning all cura new candles, amount of hours incremented by cura and curb + = cura, lets make all burnt out candles into new cura = curb / b , repeat this algorithm until we can make at least one new candle.