Tìm x biết \[25{\rm{\% }}.x - 70\frac:\left( {\frac + \frac + \frac + \frac} \right) = - 5\]

Ta có: \[25{\rm{\% }}.x - 70\frac:\left( {\frac + \frac + \frac + \frac} \right) = - 5\]

\[\frac{1}{4}x - 70\frac:\left( {\frac + \frac + \frac + \frac} \right) = - 5\]

\[25{\rm{\% }}.x - 70\frac:\left( {\frac + \frac + \frac + \frac} \right) = - 5\]

\[25{\rm{\% }}.x - 70\frac:\left[ {13.\left( {\frac{1} + \frac{1} + \frac{1} + \frac{1}} \right)} \right] = - 5\]

\[25{\rm{\% }}.x - 70\frac:\left[ {\frac{2}.\left( {\frac{1}{3} - \frac{1}{5} + \frac{1}{5} - \frac{1}{7} + \frac{1}{7} - \frac{1}{9} + \frac{1}{9} - \frac{1}} \right)} \right] = - 5\]

\[25{\rm{\% }}.x - 70\frac:\left[ {\frac{2}.\left( {\frac{1}{3} - \frac{1}} \right)} \right] = - 5\]

\[25{\rm{\% }}.x - 70\frac:\left( {\frac{2}.\frac{8}} \right) = - 5\]

\[\begin{array}{*{20}{l}}{25{\rm{\% }}.x - \frac:\frac = - 5}\\{25{\rm{\% }}.x - \frac.\frac = - 5}\\{25{\rm{\% }}.x - 45 = - 5}\\{25{\rm{\% }}.x = - 5 + 45}\\{25{\rm{\% }}.x = 40}\\{x = 40:\frac}\\{x = 160}\end{array}\]

Đáp án cần chọn là: D