[tex]v=\frac{s}{t},\ where\ V-speed,\ s-distance,\ t-time\\v*t=s\\\\
\left \{ {{v_1*t_1=s} \atop {v_2*t_2=s}} \right.\\\\t_1=6,5-t_2\\\\ \left \{ {{220(6,5-t_2)=s} \atop {280*t_2=s}} \right. \\\\
220(6,5-t_2)=280*t_2\\
1430-220t_2=280t_2\ \ \ |Add\ 220t_2\\
1430=500t_2\ \ \ |Divide\ by\ 500\\t_2=2,86h\\\\
s=t_2*v_1\\
s=2,86*280=800,8\\
2s=1601,6miles\\\\
Plane\ flew\ 1601,6\ miles\ in\ round\ trip.[/tex]