Andreea =a
Cristina = c
Nicoleta =n
a=3c
a= n-7
n= a+7 = 3c +7
a+c+n = 77
3c +c + 3c +7=77
7c+7=77
7c=77-7
7c =70
c= 70:7
c= 10
a=3c = 3×10=30
n= a+7 =30+7 =37
Verificare : 30+10+37 = 77
Raspuns : Andreea are 30 agrafe
Cristina are 10 agrafe
Nicoleta are 37 agrafe