Question

3 stilouri si 4 carti costa 120 de lei , 7 stilouri si 3 carti costa 185 de lei.Cat costa fiecare?

Answer 1

3s+4c=120lei;
7s+3c=185lei;
⇒[7s-3s]+[4c-3c]=185lei-120lei
⇒4s+c=65lei;
⇒s,c∈[[16,1][15,5][14,11][13,13][12,17][11,22]etc. toate variantele posibile;