Đáp án đúng: D
Giải chi tiết:\(\begin{array}{l}70 - 5\left( {x - 3} \right) = 45\\\,\,\,\,\,\,\,\,\,\,\,5\left( {x - 3} \right) = 75 - 45\\\,\,\,\,\,\,\,\,\,\,\,5\left( {x - 3} \right) = 25\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x - 3 = 5\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\, = 5 + 3\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\,\, = 8\end{array}\)
Vậy \(x = 8\).
Chọn D.