To identify the restrictions on the domain of the rational expression \( \frac{7x}{5x + 7} \), we need to find the values of \( x \) that make the denominator equal to zero, since division by zero is undefined.
Set the denominator equal to zero:
\[ 5x + 7 = 0 \]
Now, solve for \( x \):
\[ 5x = -7 \] \[ x = -\frac{7}{5} \]
Thus, the restriction to the domain is \( x = -\frac{7}{5} \).
In the options given, the answer is:
- -7/5