1. Let's understand the problem: You want to know when to use subtraction (-) or addition (+) in math problems. 2. The basic rule is: Use addition (+) when you are combining or increasing quantities. 3. Use subtraction (-) when you are taking away or finding the difference between quantities. 4. For example, if you have 5 apples and get 3 more, you add: $5 + 3 = 8$ apples. 5. If you have 8 apples and give away 3, you subtract: $8 - 3 = 5$ apples. 6. In equations, look at the context: Are you adding more or removing some? That tells you whether to use + or -. 7. Also, in algebra, when solving equations, you use + or - to isolate variables by doing the opposite operation. 8. Remember, addition increases or combines, subtraction decreases or finds difference. This simple rule helps decide when to use + or - in math problems.