Visual representation of adding 256 and 137 using an open number line method.

Let’s solve this step by step.

We are adding:
256 + 137

The number line shows we’re breaking 137 into parts to make it easier:
- First, add 100 → 256 + 100 = 356
- Then, add 10 → 356 + 10 = 366
- Then, add 1 → 366 + 1 = 367
- But wait — 137 is 100 + 30 + 7, not 100 + 10 + 1!

Oops — the image only added 100 + 10 + 1 = 111 so far. That means we still need to add the rest of 137.

Let’s fix that.

137 = 100 + 30 + 7

So after adding 100 (to get 356), we should add 30, then 7.

Step-by-step:

Start at 256.

→ Add 100:
256 + 100 = 356

→ Add 30:
356 + 30 = 386

→ Add 7:
386 + 7 = 393

Let’s double-check with regular addition:

```
256
+ 137
------
393
```

Yes! 6 + 7 = 13 (write 3, carry 1)
5 + 3 + 1 = 9
2 + 1 = 3
→ 393

Final Answer:
393