Răspuns :
[tex] \left \{ {{x-y = 20} \atop {[tex] \left \{ {4/3*y -y = 20} \atop {x=4/3*y}} \right. [/tex]}} \right. [/tex]
[tex] \left \{ {{1/3*y =20} \atop {x=4/3*y}} \right. [/tex]
[tex] \left \{ {{y=60} \atop {x=80}} \right. [/tex]
[tex] \left \{ {{1/3*y =20} \atop {x=4/3*y}} \right. [/tex]
[tex] \left \{ {{y=60} \atop {x=80}} \right. [/tex]