What was the question for this implicit rationale, and corresponding answer?
He saved money for 2 years, which is equal to 12 x 2 = 24 months. The amount of money he saved is $25 * 24 = $600. But he spent some money so there is $600 - $400 = 200 left.
 The answer: 200
The question: John puts $25 in his piggy bank every month for 2 years to save up for a vacation. He had to spend $400 from his piggy bank savings last week to repair his car. How many dollars are left in his piggy bank?