Multiply: (1/7x-1/8y)(7x^2-8y^2)

Dear student,
Here is the solution of your asked query:
$$\begin{gathered} \left(\frac{1}{7}\mathrm{x}-\frac{1}{8}\mathrm{y}\right)\left(7{\mathrm{x}}^2-8{\mathrm{y}}^2\right) \\ =\frac{1}{7\mathrm{x}}\left(7{\mathrm{x}}^2-8{\mathrm{y}}^2\right)-\frac{1}{8}\mathrm{y}\left(7{\mathrm{x}}^2-8{\mathrm{y}}^2\right) \\ =\frac{1}{7\mathrm{x}}\times 7{\mathrm{x}}^2-\frac{1}{7\mathrm{x}}\times 8{\mathrm{y}}^2-\frac{1}{8}\mathrm{y}\times 7{\mathrm{x}}^2+\frac{1}{8}\mathrm{y}\times 8{\mathrm{y}}^2 \\ =\mathrm{x}-\frac{8{\mathrm{y}}^2}{7\mathrm{x}}-\frac{7{\mathrm{x}}^2\mathrm{y}}{8}+{\mathrm{y}}^3 \end{gathered}$$
Regards