Ramon runs the marketing department at his company. His department gets a budget every year, and every year, he must spend the entire budget without going over. If he spends less than the budget, then his department gets a smaller budget the following year. At the beginning of this year, Ramon got $\$ 2.5$ million for the annual marketing budget. He must spend the budget such that $2,500,000-x=0 .$ What property of addition tells us what the value of $x$ must be?