Which of the following is unlike fractions to $\frac{5}{7}$?

The fraction with a different denominator is an unlike fraction.

So, fractions $\frac{2}{7}$, $\frac{4}{7}$ and $\frac{6}{7}$ are like fractions to $\frac{5}{7}$.

But $\frac{5}{9}$ is unlike fraction to $\frac{5}{7}$.

Thus, $\frac{5}{9}$ is the only unlike fraction to $\frac{5}{7}$.