use each digit from 1 to 9 to make each line sum to 15. se each digit once.
To find a solution to this problem, we can use a technique called trial and error. Here's how you can go about it:
1. Start by placing the number 5 in the center since it is the only number that can be added to any other number and still result in 15.
* This will give us the following pattern:
```
A B C
D 5 E
F G H
```
2. Next, we need to find pairs of numbers that sum to 15. Start with the corners, as they have fewer options.
* Let's start with the top left corner (A). You can try different combinations to find two numbers that sum up to 15.
* Here are a few examples:
* Option 1: 9 and 1
* Option 2: 8 and 2
* Let's say we choose Option 1. We'll place 9 in A and 1 in B.
```
9 1 C
D 5 E
F G H
```
3. Now, let's move on to the top right corner (C).
* The only number left that hasn't been used is 8, so we can place 8 in C.
```
9 1 8
D 5 E
F G H
```
4. Next, let's move to the bottom left corner (F).
* We need to find two numbers that sum up to 15, but the only remaining digit is 7. So, we can place 7 in F.
```
9 1 8
D 5 E
7 G H
```
5. Now, we can place the remaining digits into the empty cells while ensuring that each digit is used only once and that the sums on each line equal 15.
* We can complete the puzzle as follows:
```
9 1 8
6 5 4
7 2 3
```
And there you have it! Each line in the grid sums up to 15, and each digit from 1 to 9 is used only once.