1. The problem asks to write subtraction number sentences based on the given graphs. 2. The subtraction formula is $a - b = c$, where $a$ and $b$ are the numbers at the top connected to the circle below with number $c$. 3. For problem 1, the numbers are 9 and 6, and the circle below shows 3. So, the subtraction sentence is: $$9 - 6 = 3$$ 4. For problem 2, the numbers are 10 and 9, and the circle below shows 1. So, the subtraction sentence is: $$10 - 9 = 1$$ 5. Problems 3 and 4 have empty circles and boxes, so you need to fill in numbers that satisfy the subtraction sentence $a - b = c$ based on the numbers you choose or are given. 6. The key rule is that the top two numbers subtract to give the number in the circle below. 7. This exercise helps understand subtraction as the difference between two numbers. Final answers: 1) $9 - 6 = 3$ 2) $10 - 9 = 1$