Question: Can you guide me through solving this problem: James decides to buy birthday candles for his 2 sons.  One of them is 12 and the other is 4 years younger.  A pack of 5 candles costs $3.  How much does James spend on candles?
Answer: 
His younger son is 12-4=8 years old
So he needs 12+8=20 candles
That means he needs 20/5=4 packs of candles
The total cost of those is 4*3=$12