1. The problem is to explain a Primary 4 math concept in a simple way. 2. Since the user did not specify a particular problem, I will explain a basic concept suitable for Primary 4: addition and subtraction of two-digit numbers. 3. The formula for addition is $a + b = c$, where $a$ and $b$ are numbers and $c$ is their sum. 4. For subtraction, the formula is $a - b = c$, where $a$ is the number you start with, $b$ is the number you take away, and $c$ is what remains. 5. Example: Add 23 and 45. 6. Step 1: Add the ones place: $3 + 5 = 8$. 7. Step 2: Add the tens place: $20 + 40 = 60$. 8. Step 3: Add the results: $60 + 8 = 68$. 9. So, $23 + 45 = 68$. 10. Example: Subtract 15 from 42. 11. Step 1: Subtract the ones place: $2 - 5$ cannot be done, so borrow 1 ten (which is 10) from the tens place. 12. Step 2: Now, $12 - 5 = 7$. 13. Step 3: Subtract the tens place: $3 - 1 = 2$ (because we borrowed 1 ten earlier). 14. So, $42 - 15 = 27$. 15. This method helps understand addition and subtraction by breaking numbers into tens and ones, making it easier to calculate.