Question: Provide a step by step solution for the following math problem: Gerald and Julia divided $100 in the ratio 3:2. If Gerald spent $10 on a book, how much money did he have left?
Answer: 
The $100 was divided into 3 + 2 = 5 parts.
So each part is $100/5 = $20.
So Gerald received $20 x 3 = $60.
Gerald bought a book at $10.
Therefore, Gerald was left with $60 - $10 = $50.