The expression you've provided is an equation that we can solve for \( x \). The equation is:

\[
x = -\frac{5}{7} + \frac{7}{9}
\]

To solve for \( x \), we need to perform the arithmetic operations on the right side. First, find a common denominator for the fractions \(-\frac{5}{7}\) and \(\frac{7}{9}\). The least common denominator between 7 and 9 is 63.

Convert each fraction to have this common denominator:

1. \(-\frac{5}{7} = -\frac{5 \times 9}{7 \times 9} = -\frac{45}{63}\)
2. \(\frac{7}{9} = \frac{7 \times 7}{9 \times 7} = \frac{49}{63}\)

Now, subtract these fractions:

\[
x = -\frac{45}{63} + \frac{49}{63} = \frac{49 - 45}{63} = \frac{4}{63}
\]

Thus, \( x = \frac{4}{63} \).