(a) $\displaystyle\frac{3}{4}-\frac{1}{12}-\frac{5}{6}$; (b) $\displaystyle\frac{3}{2}+\frac{15}{4}-\frac{7}{3}$; (c) $\displaystyle\frac{2}{5}\left(\frac{5}{2}-\frac{8}{3}\right)$; (d) $\displaystyle\frac{2}{7}\div \frac{5}{2}$; (e) $\displaystyle\left(\frac{2}{3}\right)^3\times \left(\frac{2}{3}\right)^2$; (f) $\displaystyle\left(\frac{5}{7}\right)^5\times \left(-\frac{7}{10}\right)^5$; (g) $\displaystyle\left[\left(\frac{2}{5}\right)^2\right]^3$; (h) $\displaystyle 5-\left[\left(\frac{-2}{5}\right)^2\right]^0$; (i) $\displaystyle\left(-\frac{1}{3}\right)^{-2}$; (j) $\displaystyle\frac{2^3}{\left(\frac{1}{2}\right)^4}$; (l) $\displaystyle\left(-\frac{1}{3}\right)^{-3}\div \left(\frac{5}{3}\right)^3$; (l) $\displaystyle\left(\frac{2}{5}\right)^{0}\times \left(-\frac{5}{2}\right)^{-2}$.