Answer
a. 0
b. $\{ 8 \}$
Work Step by Step
$\frac{4}{x}= \frac{9}{5} - \frac{7x-4}{5x}$
a. $x =0 $ makes the denominator zero. So, $ x = 0$ is the restricted value.
b. $\frac{4}{x}= \frac{9}{5} - \frac{7x-4}{5x}; x \ne 0;$
Take LCD at right hand side.
$\frac{4}{x}= \frac{9x-(7x-4)}{5x}; x \ne 0;$
$\frac{4}{x}= \frac{9x-7x+4}{5x}; x \ne 0;$
$\frac{4}{x}= \frac{2x+4}{5x}; x \ne 0;$
Multiply both sides by $5x$.
$5x(\frac{4}{x})= 5x(\frac{2x+4}{5x}); x \ne 0;$
$20 = 2x+4$
$20-4 = 2x$
$2x = 16$
$x = 8$
$8$ is not the restricted value.
Solution set $:\{8 \}$