Question 131
Vitalii, Michael and Olexandr were given $n$ dollars by their mother each one. Vitalii had to spend all his money for buying books, Michael for buying notebooks, Olexandr for pens. Vitalii had bought 1 book, Michael 2 notebooks and Olexandr 5 pens. After that, they together had $n$ dollars. Prove that one of the boys can buy one more item.