Đáp án đúng: C
Giải chi tiết:\(\begin{array}{l}\,\frac{8}{5} - \frac{3}{5}:x = 0,4\\\,\,\,\,\,\frac{8}{5} - \frac{3}{5}:x = \frac{2}{5}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{3}{5}:x = \frac{8}{5} - \frac{2}{5}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{3}{5}:x = \frac{6}{5}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = \frac{3}{5}:\frac{6}{5}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = \frac{1}{2}\end{array}\)
Vậy \(x = \frac{1}{2}\)
Chọn C