[tex] \left \{ {{4x+7y=10} \atop {-4x-6y=28}} \right. \\\\add\ those\ two\ equations\\\\
y=38\\\\
4x+7y=10\ \ \ | subtract\ 7y\\\\
4x=10-7x\ \ \ \ | divide\ by\ 4\\\\
x=\frac{10-7x}{4}=\frac{10-7*38}{4}=\frac{10-266}{4}=\frac{-256}{4}=-64\\\\
solution:\\ \left \{ {{y=38} \atop {x=-64}} \right. [/tex]
