Đáp án:
$\begin{array}{l}
\frac{{x - 1}}{{2015}} - \frac{{x + 3}}{{2011}} = \frac{{x + 7}}{{2007}} - \frac{{x + 11}}{{2003}}\\
\Rightarrow \frac{{x - 1}}{{2015}} + 1 - \frac{{x + 3}}{{2011}} - 1 = \frac{{x + 7}}{{2007}} + 1 - \frac{{x + 11}}{{2003}} - 1\\
\Rightarrow \frac{{x - 1 + 2015}}{{2015}} - \frac{{x + 3 + 2011}}{{2011}} = \frac{{x + 7 + 2007}}{{2007}} - \frac{{x + 11 + 2003}}{{2003}}\\
\Rightarrow \frac{{x - 2014}}{{2015}} - \frac{{x - 2014}}{{2011}} = \frac{{x - 2014}}{{2007}} - \frac{{x - 2014}}{{2003}}\\
\Rightarrow \left( {x - 2014} \right).\left( {\frac{1}{{2015}} - \frac{1}{{2011}} - \frac{1}{{2007}} + \frac{1}{{2003}}} \right) = 0\\
\Rightarrow x = 2014
\end{array}$
Vậy x=2014.
