Subtract the polynomials. \[ \left(\frac{7}{8} x^{7}-\frac{9}{7} x-\frac{2}{5}\right)-\left(\frac{3}{8} x^{7}-\frac{4}{7} x+\frac{6}{5}\right)=\square \]

To subtract the polynomials, we need to distribute the negative sign through the second polynomial and then combine like terms. Start by rewriting the expression: \[ \left(\frac{7}{8} x^{7} - \frac{9}{7} x - \frac{2}{5}\right) - \left(\frac{3}{8} x^{7} - \frac{4}{7} x + \frac{6}{5}\right) \] Distributing the negative sign gives: \[ \frac{7}{8} x^{7} - \frac{9}{7} x - \frac{2}{5} - \frac{3}{8} x^{7} + \frac{4}{7} x - \frac{6}{5} \] Now, combine the like terms. For the \(x^{7}\) terms: \[ \frac{7}{8} x^{7} - \frac{3}{8} x^{7} = \left(\frac{7}{8} - \frac{3}{8}\right)x^{7} = \frac{4}{8} x^{7} = \frac{1}{2} x^{7} \] Next, combine the \(x\) terms: \[ -\frac{9}{7} x + \frac{4}{7} x = \left(-\frac{9}{7} + \frac{4}{7}\right)x = -\frac{5}{7} x \] Finally, combine the constant terms: \[ -\frac{2}{5} - \frac{6}{5} = -\frac{8}{5} \] Putting it all together, we get: \[ \frac{1}{2} x^{7} - \frac{5}{7} x - \frac{8}{5} \] So the final answer is: \[ \frac{1}{2} x^{7} - \frac{5}{7} x - \frac{8}{5} \]