Someone stole $20 off your desk at school. You find 4 suspects: Gina, Kelly, Peter, and Liam. You ask them all about the money: Gina: Hey, I didn't take it! Kelly: I'm pretty sure Peter took it! Peter: No way! Kelly is lying! Liam: Gina's telling the truth! One of these people is telling the truth. Who took your money?
Gina took the money. She, Kelly, and Liam are lying while Peter is telling the truth. If any of the other people had taken it, then there would be only 1 liar and 3 people telling the truth.