Hi,
[tex] \left \{ {{x^2+y^2=25} \atop {2x+y=10}} \right. \\\\
\left \{ {y=10-2x} \atop {x^2+(10-2x)^2=25}} \right. \\\\
\left \{ {{5x^2-40x+100=25} \atop {y=10-2x}} \right. \\\\
\left \{ {{x^2-8x+15=0} \atop {y=10-2x}} \right. \\\\
\left \{ {{(x-3)(x-5)=0} \atop {y=10-2x}} \right. \\\\
\left \{ {{x=3} \atop {y=4}} \right. \\\\
\ or\ \\
\left \{ {{x=5} \atop {y=0}} \right. \\\\
[/tex]
