Răspuns :
a : b = 7
a - b = 30
a = b x 7
b x 7 - b = 30
6 x b = 30
b = 30 : 6
b = 5
a = b x 7 = 5 x 7 = 35
proba : a - b = 35 - 5 = 30
a - b = 30
a = b x 7
b x 7 - b = 30
6 x b = 30
b = 30 : 6
b = 5
a = b x 7 = 5 x 7 = 35
proba : a - b = 35 - 5 = 30