d) 4/5 . 3/8 + 1/8 . 4/5 - 4/5 . (-1/4)

* Hướng dẫn giải

$\begin{array}{l}\mathrm{d}) \frac{4}{5}.\frac{3}{8}+\frac{1}{8}.\frac{4}{5}-\frac{4}{5}.\left(-\frac{1}{4}\right)\\ =\frac{4}{5}.\frac{3}{8}+\frac{1}{8}.\frac{4}{5}+\frac{4}{5}.\frac{1}{4}\\ =\frac{4}{5}.\left(\frac{3}{8}+\frac{1}{8}+\frac{1}{4}\right)\\ =\frac{4}{5}.\left(\frac{4}{8}+\frac{1}{4}\right)\\ =\frac{4}{5}.\left(\frac{2}{4}+\frac{1}{4}\right)\\ =\frac{4}{5}.\frac{3}{4}\\ =\frac{3}{5}\end{array}$