a x b =126
(1) a x c = 84
(2) a x (b+c):3 =? ; a x(b-c):3 =?
Adunam ecuatia (1) cu ecuatia (2) si rezulta: a x b + a x c =126+84 = 210
adica a x (b +c) = 210
a x (b +c) :3 = 210:3 = 70
Scadem ecuatia (2) din ecuatia (1) si rezulta:
a x b - a x c = 126-84 = 42 ; adica a x (b-c) = 42
a x (b-c) :3 = 42:3 = 14