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To estimate the expression \( 523.7 - 267.9 \) by rounding to the nearest hundred:

1. **Round 523.7** to the nearest hundred:
- 523.7 rounds to **500**.

2. **Round 267.9** to the nearest hundred:
- 267.9 rounds to **300**.

Now rewrite the problem using the estimates:

\( 500 - 300 \)

Now, calculate the estimated answer:

\( 500 - 300 = 200 \)

So, the estimated answer is **200**.