Ten people are sitting in a row, and each is thinking of a negative integer no smaller than $-15$. Each person subtracts, from his own number, the number of the person sitting to his right (the rightmost person does nothing). Because he has nothing else to do, the rightmost person observes that all the differences were positive. Let $x$ be the greatest integer owned by one of the 10 people at the beginning. What is the minimum possible value of $x$?
I was completely thrown off this problem because of the sentence, "Let $x$ be the greatest integer owned by one of the 10 people at the beginning.", which I intepretted as the first value we start with is -1, because the largest negative integer is -1. It doesn't even come off as ambigious, and yet, to find the minumum value of x, the first value needs to be -15. So, I'm curious at what I'm missing here. Word problems have never been my forté, so any advice on how one should approach these types of questions would be appreciated. Thanks!