Question

trei caiete si patru pixuri costa 16,50 lei iar foua caiete di trei pixuri costa 11,50 .cati lei costaun caiet si cati lei costa un pix

Answer 1

x=preț caiet
y=pret pix
Metoda 1.
3x+4y=16.5 |x2
2x+3y=11.5 |×(-3)

6x+8y=33
-6x-9y=34.5
__________
(+) -y=-1.5 => y=1.50 lei

2x +3 ×1.5=11.5
2x + 4.5=11.5
2x=7
x=3.50 lei
Metoda 2.
3x=16.5-4y
x=(16.5-4y):3

2×[(16.5-4y):3]+3y=11.5
2×(16.5-4y)+9y=34.5
33-8y+9y=34.5
y=34.5-33
y=1.5 lei

x=(16.5-4×1.5)÷3=(16.5-6)÷3=10.5÷3=3.5