Question

Daca 9 lazi cu portocale si 3 lazi cu lamai cantaresc in total 63 de kilograme, iar 3 lazi cu portocale si 4 lazi cu lamai cantaresc in total 30 de kilograme, afla cat cantaresc 5 lazi cu lamai.

Answer 1

{9p+3l=63
{3p+4l=30 |×(-3)

{9p+3l=63
{-9p-12l=-90

9p-9p+3l-12l=63-90
0-9l=-27
-9l=-27 |:(-9)
l=3
3p+4l=30
3p+4×3=30
3p+12=30
3p=30-12
3p=18
p=18:3
p=6
5l=5×3=15

Answer 2

9p+3l=63 I :3 si le scad
3p+ l = 21
3p+4l=30
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 /   3l=9
l=3
5l=5x3=15 kg