3-digit mixed addition and subtraction practice worksheet with and without regrouping.

Let's solve each of the mixed addition and subtraction problems in the image, which includes both with and without regrouping. We'll go step by step for each problem.

---

Problem 1:

```
828
+ 819
-----
```
Addition:
- 8 + 9 = 17 → write 7, carry 1
- 2 + 1 + 1 = 4
- 8 + 8 = 16

So:
828 + 819 = 1,647

---

Problem 2:

```
823
+ 789
-----
```
- 3 + 9 = 12 → write 2, carry 1
- 2 + 8 + 1 = 11 → write 1, carry 1
- 8 + 7 + 1 = 16

So:
823 + 789 = 1,612

---

Problem 3:

```
787
- 755
-----
```
Subtraction:
- 7 - 5 = 2
- 8 - 5 = 3
- 7 - 7 = 0

So:
787 - 755 = 32

---

Problem 4:

```
603
+ 906
-----
```
- 3 + 6 = 9
- 0 + 0 = 0
- 6 + 9 = 15

So:
603 + 906 = 1,509

---

Problem 5:

```
835
- 677
-----
```
Subtraction with regrouping:
- 5 < 7 → borrow from tens: 15 - 7 = 8
- 2 (after borrowing) < 7 → borrow from hundreds: 12 - 7 = 5
- 7 (after borrowing) - 6 = 1

So:
835 - 677 = 158

---

Problem 6:

```
342
- 329
-----
```
- 2 < 9 → borrow: 12 - 9 = 3
- 3 (after borrowing) < 2 → borrow: 13 - 2 = 11? Wait — let’s do it carefully:

Actually:
- Units: 2 < 9 → borrow from tens → 12 - 9 = 3
- Tens: 3 becomes 2, but 2 < 2? No — wait, 2 - 2 = 0?
Wait: original tens digit is 4 → we borrowed 1 → now 3 → then subtract 2 → 3 - 2 = 1?

Wait, let's do it properly:

```
342
- 329
-----
```

- Units: 2 < 9 → borrow from tens → tens become 3, units become 12 → 12 - 9 = 3
- Tens: 3 (after borrow) - 2 = 1
- Hundreds: 3 - 3 = 0

So: 342 - 329 = 13

---

Problem 7:

```
734
+ 342
-----
```
- 4 + 2 = 6
- 3 + 4 = 7
- 7 + 3 = 10

So: 734 + 342 = 1,076

---

Problem 8:

```
663
+ 433
-----
```
- 3 + 3 = 6
- 6 + 3 = 9
- 6 + 4 = 10

So: 663 + 433 = 1,096

---

Problem 9:

```
878
+ 585
-----
```
- 8 + 5 = 13 → write 3, carry 1
- 7 + 8 + 1 = 16 → write 6, carry 1
- 8 + 5 + 1 = 14

So: 878 + 585 = 1,463

---

Problem 10:

```
991
- 596
-----
```
- 1 < 6 → borrow: 11 - 6 = 5
- 8 (after borrow) < 9 → borrow: 18 - 9 = 9
- 8 (after borrow) - 5 = 3

So: 991 - 596 = 395

---

Problem 11:

```
657
+ 566
-----
```
- 7 + 6 = 13 → write 3, carry 1
- 5 + 6 + 1 = 12 → write 2, carry 1
- 6 + 5 + 1 = 12

So: 657 + 566 = 1,223

---

Problem 12:

```
602
+ 599
-----
```
- 2 + 9 = 11 → write 1, carry 1
- 0 + 9 + 1 = 10 → write 0, carry 1
- 6 + 5 + 1 = 12

So: 602 + 599 = 1,201

---

Problem 13:

```
877
- 726
-----
```
- 7 - 6 = 1
- 7 - 2 = 5
- 8 - 7 = 1

So: 877 - 726 = 151

---

Problem 14:

```
674
+ 397
-----
```
- 4 + 7 = 11 → write 1, carry 1
- 7 + 9 + 1 = 17 → write 7, carry 1
- 6 + 3 + 1 = 10

So: 674 + 397 = 1,071

---

Problem 15:

```
472
- 313
-----
```
- 2 < 3 → borrow: 12 - 3 = 9
- 6 (after borrow) - 1 = 5
- 4 - 3 = 1

So: 472 - 313 = 159

---

Problem 16:

```
889
- 855
-----
```
- 9 - 5 = 4
- 8 - 5 = 3
- 8 - 8 = 0

So: 889 - 855 = 34

---

Problem 17:

```
989
- 982
-----
```
- 9 - 2 = 7
- 8 - 8 = 0
- 9 - 9 = 0

So: 989 - 982 = 7

---

Problem 18:

```
400
+ 396
-----
```
- 0 + 6 = 6
- 0 + 9 = 9
- 4 + 3 = 7

So: 400 + 396 = 796

---

Problem 19:

```
310
+ 563
-----
```
- 0 + 3 = 3
- 1 + 6 = 7
- 3 + 5 = 8

So: 310 + 563 = 873

---

Problem 20:

```
616
- 345
-----
```
- 6 - 5 = 1
- 1 < 4 → borrow: 11 - 4 = 7
- 5 (after borrow) - 3 = 2

So: 616 - 345 = 271

---

✔ Final Answers:

| Problem | Answer |
|--------|--------|
| 1 | 1,647 |
| 2 | 1,612 |
| 3 | 32 |
| 4 | 1,509 |
| 5 | 158 |
| 6 | 13 |
| 7 | 1,076 |
| 8 | 1,096 |
| 9 | 1,463 |
| 10 | 395 |
| 11 | 1,223 |
| 12 | 1,201 |
| 13 | 151 |
| 14 | 1,071 |
| 15 | 159 |
| 16 | 34 |
| 17 | 7 |
| 18 | 796 |
| 19 | 873 |
| 20 | 271 |

---

🔍 Explanation Summary:

- For addition, we add digits from right to left, carrying over when the sum exceeds 9.
- For subtraction, we subtract digit by digit, borrowing from the next higher place if needed.
- Some problems involve regrouping (borrowing or carrying), especially when a digit is too small to subtract or when the sum exceeds 9.

Let me know if you'd like this formatted as a printable worksheet or want to check any specific problem!