s=pretul unui stilou
p=pretul unui pix
2s+7p=41 -rel 1
4s+9p=67 -rel 2
inmultesti relatia 1 cu 2
4s+14p=82
4s+9p=67
scazi relatiile
4s+14p-4s-9p=82-67
5p=15
p=15/5=3
revenim in relatia 1 initiala:
2s+7 ori 3=41
2s+21=41
2s=41-21
2s=20
s=20/2=10
2s+7p=41lei /(×-2)
4s+9p=67lei
=> -4s-14p= -82
4s+9p=67
_____________
/ -5p=-15/ ×(-1)
5p=15 => p=3( lei costa un pix)
inlocuiesti in prima relatie
2s+21=41
2s=41-21
2s=20 => s=10(lei costa un stilou)
