Question

Diana a cumparat 3.5 kg mere si 2 kg rosii si a platit 24 lei. Luca a cumparat 7 kg mere si 1.5 kg rosii si a platit 35.5 lei.
Cat costa un kg de mere?
Dar de rosii? dau coroana

Answer 1

$\left \{ {{3,5x+2y=24} \atop {7x+1,5y=35,5}} \right. \\ \left \{ {{[3,5x+2y=24]\cdot2} \atop {7x+1,5y=35,5}} \right. \\ \\ \left \{ {{7x+4y=48 \atop {7x+1,5y=35,5}} \right.$
se scad

$\left \ {{7x-7x+4y-1,5y=48-35,5$
$2,5y=12,5;\\ \\ y=12,5:2,5 \\ \\ y=5$

$3,5x+2y=24 ; y=5 \\ \\ 3,5x+2\cdot5=24 \\ \\ 3,5x=14 \\ \\ x=4$

mere = 5 lei/kg  iar rosii = 4/ lei kg