\[ \boxed { \left \{ {\frac {\rm d}{{\rm d}t}}x \left ( t \right ) +3\,x \left ( t \right ) +4\,y \left ( t \right ) =0,{\frac {\rm d}{{\rm d}t}}y \left ( t \right ) +2\,x \left ( t \right ) +5\,y \left ( t \right ) =0 \right \} } \]
Mathematica: cpu = 0.007001 (sec), leaf count = 84 \[ \left \{\left \{x(t)\to \frac {1}{3} c_1 e^{-7 t} \left (2 e^{6 t}+1\right )-\frac {2}{3} c_2 e^{-7 t} \left (e^{6 t}-1\right ),y(t)\to \frac {1}{3} c_2 e^{-7 t} \left (e^{6 t}+2\right )-\frac {1}{3} c_1 e^{-7 t} \left (e^{6 t}-1\right )\right \}\right \} \]
Maple: cpu = 0.031 (sec), leaf count = 35 \[ \left \{ \left \{ x \left ( t \right ) ={\it \_C1}\,{{\rm e}^{-t}}+{\it \_C2}\,{{\rm e}^{-7\,t}},y \left ( t \right ) =-{\frac {{\it \_C1}\,{ {\rm e}^{-t}}}{2}}+{\it \_C2}\,{{\rm e}^{-7\,t}} \right \} \right \} \]