Đáp án đúng: C
Giải chi tiết:\(\begin{array}{l}x:9 + 2009 = 5261\\x:9\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 5261 - 2009\\x:9\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \,3252\\x\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 3252 \times 9\\x\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 29\,268\end{array}\)
Vậy \(x = 29\,268\).
Chọn C.