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