Đáp án đúng: B
Giải chi tiết:\(\begin{array}{l}36000:x = 5600:70\\36000:x\, = \,560:7\\36000:x\, = \,80\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\, = 36000:80\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = 3600:8\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = 450\end{array}\)
Vậy \(x = 450\)
Chọn B.