\[
\boxed{
 \left\{ {\frac {{\rm d}^{2}}{{\rm d}{t}^{2}}}x \left( t \right) +6\,x \left( t \right) +7\,y \left( t \right) =0,{\frac {{\rm d}^{2}}{{\rm d}{t}^{2}}}y \left( t \right) +3\,x \left( t \right) +2\,y \left( t \right) =2\,t \right\} }
\]