Bonjour,

2ch + 5cr = 6,70

2ch = 6,70 - 5cr

6ch+ 6cr = 13,80

6ch = 3(6,70 -5cr)

  =>

3(6,70 -5cr) +6cr = 13,80

20,10 - 15cr +6cr = 13,80

20,10 -  -13,80 = 15cr - 6cr

6,30 = 9 cr
cr = 6,30 / 9

1 croissant = 0,70€

2ch + 5cr = 6,70

2ch + ( 5*0,70) = 6,70

2ch + 3,50 = 6,70

2ch = 6,70 - 3,50

2 ch =3,20

1 ch = 3,20/2

1ch = 1,60

1 chocolatine = 1,60€