Đáp án đúng: D
Giải chi tiết:\(\begin{array}{l}\,\,\,5 + \frac{2}{3}:x = 7\\\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{2}{3}:x\, = 7 - 5\\\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{2}{3}:x = 2\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = \frac{2}{3}:2\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = \frac{1}{3}\end{array}\)
Chọn D