When Mulla ran a small shop, he used to let people buy on credit and wrote their debts in a ledger. One day, a guy who owed him money was walking past his house. Mulla called him over. "Do you know how long you've owed me money? It's time to pay up." The guy, knowing Mulla was relentless, sighed. "Fine. Bring the ledger, let's see what I owe." Excited, Mulla brought the book and calculated the debt: 31 coins. The guy looked at the ledger and noticed that his neighbor also owed Mulla 25 coins. Thinking fast, he said, "Mulla, my neighbor owes you 25 coins. Subtract his debt from my debt. 31 minus 25 is 6 coins. I'll give you the 6 coins right now, and we'll just cross both of our names out of the book." Mulla, who loved settling accounts, thought this was brilliant. He took the 6 coins, crossed both names out, and gave the man a receipt saying both debts were cleared. He proudly went to his wife and said, "I just easily collected two debts at once!" His wife realized he had been scammed and dragged him to the judge. The judge summoned the debtor and asked, "What kind of fake math did you just pull on Mulla?" The man laughed. "I didn't have the cash, and I knew he'd make a scene, so I made a joke. But he actually fell for it!" The judge forced the man to sign a real IOU for the remaining debt, handed it to Mulla, and said, "Mulla, please, since you clearly don't know how math works, ask for help next time so I don't have to deal with this."