a) ($\frac{2}{5}$+ $\frac{5}{6}$)×$\frac{3}{4}$
= ($\frac{24}{60}$ + $\frac{50}{60}$)×$\frac{45}{60}$
= $\frac{74}{60}$×$\frac{45}{60}$
= $\frac{3330}{3600}$
= $\frac{111}{120}$
b) $\frac{7}{12}$×$\frac{4}{5}$+$\frac{3}{2}$×$\frac{4}{5}$
= $\frac{4}{5}$×($\frac{7}{12}$+$\frac{3}{2}$)
= $\frac{4}{5}$×$\frac{25}{12}$
= $\frac{100}{60}$
= $\frac{5}{3}$
