\left \{ {{\frac{1}{2}x+\frac{1}{5}y=7 } \atop {\frac{3}{5}x-\frac{2}{3}y=22}} \right.
\left \{ {{5x+2y=70 } \atop {9x-10y=330}} \right.
\left \{ {{5x=70-2y } \atop {9x-10y=330}} \right.
\left \{ {{x=\frac{70-2y}{5} } \atop {9x-10y=330}} \right.
\left \{ {{x=14-0,4y } \atop {9(14-0,4y)-10y=330}} \right.
\left \{ {{x=14-0,4y } \atop {126-3,6y-10y=330}} \right.
\left \{ {{x=14-0,4y } \atop {126-13,6y=330}} \right.
\left \{ {{x=14-0,4y } \atop {-13,6y=330-126}} \right.
\left \{ {{x=14-0,4y } \atop {-13,6y=204}} \right.
\left \{ {{x=14-0,4y } \atop {-13,6y=204}} \right.
\left \{ {{x=14-0,4y } \atop {y=-15}} \right.
\left \{ {{x=14-0,4(-15) } \atop {y=-15}} \right.
\left \{ {{x=14+6} \atop {y=-15}} \right.
\left \{ {{x=20} \atop {y=-15}} \right.