To determine which of these differences would result in a rational number, we need to evaluate each option one by one:
1. **\(\sqrt{64} - \sqrt{7}\)**:
- \(\sqrt{64} = 8\) (rational)
- \(\sqrt{7}\) is irrational.
- Thus, \(8 - \sqrt{7}\) is irrational.
2. **\(\sqrt{49} - \frac{1}{4}\)**:
- \(\sqrt{49} = 7\) (rational)
- \(\frac{1}{4}\) is also rational.
- Thus, \(7 - \frac{1}{4} = 7 - 0.25 = 6.75\) (rational).
3. **\(\sqrt{5} - 3.2\)**:
- \(\sqrt{5}\) is irrational.
- \(3.2\) is rational.
- Thus, \(\sqrt{5} - 3.2\) is irrational.
4. **\(6.2\overline{6} - \pi\)**:
- \(6.2\overline{6}\) is a rational number (specifically, it is equal to \(6 \frac{2}{3}\)).
- \(\pi\) is irrational.
- Thus, \(6.2\overline{6} - \pi\) is irrational.
The only difference that results in a rational number is:
**\(\sqrt{49} - \frac{1}{4}\)**, which equals \(6.75\).