Bonjour,
Calculer:
6/9 + 7/99= 2/3 + 7/99= (2x33+7)/99= (66+7)/99= 73/99
90/90-7/9= 1-7/9= (1x9-7)/9= (9-7)/9= 2/9
68/77-3/7= (68-3x11)/77= 35/77= (35:7)/(77:7)= 5/11
4/7+6/21= 4/7+2/7= 6/7
