A British mother sharedthis puzzler via social media, saying her student (in second grade) was asked to answer it. There are some people on a train; 19 people get off the train at the first stop, and 17 get on the train. Now, there are 63 people on the train. How many people were there to begin with?
Correct answer: 65. Here's the explanation: -19 + 17 = -2, so ultimately, two people got off the train, and originally, the train had two more people.