1. Let's start by understanding what you want to learn. Since you said "Can you explain it in grade 4," I will explain a simple math problem in a way a 4th grader can understand. 2. Suppose we want to solve this problem: What is 8 plus 5? 3. The formula for addition is simple: $a + b = c$, where $a$ and $b$ are numbers you add, and $c$ is the answer. 4. So here, $8 + 5 = ?$ 5. To solve, count 8 objects, then count 5 more objects, and see how many you have in total. 6. When you count all together, you get $13$. 7. So, $8 + 5 = 13$. 8. This is how addition works: you put two groups together and count all the items. 9. Remember, addition means putting things together to find out how many there are in total. 10. That's the answer!