a+b+c=57 (1)
2a+b+2c=73 (2)
scadem din relatia (2) relatia (1)
2a+b+2c-(a+b+c)=73-57 ⇒2a+b+2c-a-b-c=16 ⇒ a+c=16
a+b+c=57 (1)
2a+b+2c=73 inmultim cu 3
6a+3b+6c=73×3 ⇒6a+3b+6c=219 (2)
scadem din relatia (2) relatia (1)
6a+3b+6c-(a+b+c)=219-57
6a+3b+6c-a-b-c=162
5a+2b+5c=162
(a+c)×(5a+2b+5c)
=16×162=2592