1. Let's start by understanding the problem: Johnny has some apples, and we want to find out how many he has left after some are taken away or used. 2. The key formula to use here is subtraction: $$\text{Apples left} = \text{Initial apples} - \text{Apples taken away}$$ 3. Important rule: Always subtract the number of apples taken away from the initial number of apples Johnny had. 4. For example, if Johnny had 10 apples and he gave away 3, then: $$\text{Apples left} = 10 - 3$$ 5. Simplify the subtraction: $$\text{Apples left} = 7$$ 6. So Johnny has 7 apples left. 7. If the problem is more complicated, like Johnny eats some apples and then buys more, you just add or subtract step by step, always keeping track of how many apples Johnny has at each step. This way, you can solve any problem about how many apples Johnny has left by carefully adding or subtracting the amounts given.