Bonjour,
x: iris
y: roses
15x + 6y = 39
5x+ 8y = 25
5x = 25 -8y
15x =3*5x
3( 25 -8y) +6y = 39
75 -24y +6y= 39
75-39 = 24y - 6y
36 = 18y
y= 36/18 = 2
Roses: 2€
Iris :
15x + 6y = 39
15x + 12 = 39
15x = 39-12
15x = 27
x= 27/15 =1,80€
iris = 1,80€
Vérif:
15* 1,80 + 6*2= 27+12 = 39
Réponse :
On appel les roses x et les iris y
15y + 6x = 39
5y + 8x = 25
5y + 2x = (15y + 6x) / 3 = 39 / 3 = 13
6x = 5y + 8x - 5y + 2x = 25 - 13 = 12
x = 6x / 6 = 12 / 6 = 2
5y = 5y + 8x - 8x = 25 - 16 = 9
y = 5y / 5 = 9 / 5 = 1.8
Une iris coute 1.8 € et la rose coute 2 €