Tìm x, biết: \(\,0,6.x + 40\% x = 9\)

* Hướng dẫn giải

\(\begin{array}{l}\,0,6.x + 40\% .x = 9\\\,\,\,\,\,0,6.x\, + \,0,4.x\,\,\,\, = 9\\\,\,\,\,\,\,\left( {0,6 + 0,4} \right).x\,\,\, = 9\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\, = 9\end{array}\)

Chọn D