Question

5 carti si 3 albume costa 195 lei, iar 3 carti si 5 albume costa 165 lei. Aflati cat costa o carte. Dar un album?

Answer 1

presupunem ca o carte-x, iar un album-y:
aflam y:
5x+3y=195
5y+3x=165
3×5x+3×3y=3×195
5×3x+5×5y=165
15x+9y=585
15x+25y=825
(-16) y=-240
y= -240/(-16)
y=15×(-16)/(-16)
y=15
aflam x:
5x+3×15=195
5x+45=195
5x=195-45
5x=150
x=150:5
x=30
astfel:
1 album= 15
1 carte= 30