Sustración: x-y=d
[tex] \left \{ {{x+y=400} \atop {x-y=x+80}} \right. [/tex]
[tex] \left \{ {{x+y=400} \atop {2x=480+x}} \right. [/tex]
[tex] \left \{ {{x+y=400} \atop {x=480}} \right. [/tex]
[tex] \left \{ {{y=400-480} \atop {x=480}} \right. [/tex]
[tex] \left \{ {{y=-80} \atop {x=480}} \right. [/tex]
Los números son: -80 y 480.