The phrase "decreased by" means subtraction. Also whenever you see "a number", you can think of x. So we have 125 - x is the answer. Just be careful in this section, the terms "from" and "less than" will require you to change the order that you see in the question. For us, the phrase was "decreased by" so we didn't need to change the order. The 125 was in front and the "number" was in the back. EXTRA: "125 from a number" would be x - 125 because you would have to switch the order.