Răspuns :
Explicație pas cu pas:
x= pret stilou
y= pret pix
7x+6y=156
2×+3y=51=>3y=51-2×
5×+3y=105
5×+51-2×=105
3×=54
×=18
3y=51-36=15=>y=5
Răspuns:
7stilouri......6pixuri......156lei
2stilouri.....3pixuri.......51lei/×2
7stilouri.....6pixuri.......156lei
4stilouri.....6pixuri.......102lei
3stilouri........../............. 54lei
1 stilou..............................54:3=18 lei
1 pix..................................(de aici nu mai stiu, scuuuuuuuuuuzeeeeeee)