\[ \left \{x'(t)+2 x(t)+y'(t)+y(t)=t+e^{2 t},x'(t)-x(t)+y'(t)+3 y(t)=e^t-1\right \} \] ✓ Mathematica : cpu = 0.0947238 (sec), leaf count = 118
\[\left \{\left \{x(t)\to \frac {1}{5} \left (t-e^t+e^{2 t}+1\right )+\frac {5}{72} \left (\frac {12 \left (5712 t+833 e^t+2352 e^{2 t}-5508\right )}{20825}+c_1 e^{-7 t/5}\right ),y(t)\to \frac {1}{5} \left (-t+e^t-e^{2 t}-1\right )+\frac {5}{48} \left (\frac {12 \left (5712 t+833 e^t+2352 e^{2 t}-5508\right )}{20825}+c_1 e^{-7 t/5}\right )\right \}\right \}\] ✓ Maple : cpu = 0.088 (sec), leaf count = 51
\[ \left \{ \left \{ x \left ( t \right ) ={\frac {3\,t}{7}}-{\frac {1}{49}}-{\frac {{{\rm e}^{t}}}{6}}+{\frac {5\,{{\rm e}^{2\,t}}}{17}}+{{\rm e}^{-{\frac {7\,t}{5}}}}{\it \_C1},y \left ( t \right ) =-{\frac {{{\rm e}^{2\,t}}}{17}}+{\frac {t}{7}}-{\frac {26}{49}}+{\frac {{{\rm e}^{t}}}{4}}+{\frac {3\,{\it \_C1}}{2}{{\rm e}^{-{\frac {7\,t}{5}}}}} \right \} \right \} \]