\[x - \frac{7}{x} = ?\]
\[x^{2} + \frac{49}{x^{2}} = 50\]
\[x^{2} - 14 + \frac{49}{x^{2}} = 50 - 14\]
\[\left( x - \frac{7}{x} \right)^{2} = 36\]
\[x - \frac{7}{x} = \pm 6.\]