Question

Calculati: 5a+7b+c,daca 4a+7b=840 si a+c=120

Answer 1

Este simplu, pur si simplu facem suma celor 2 ecuatii si vom avea: (4a+7b)+(a+c)=840+120 <=> 5a+7b+c= 960.

Answer 2

4a+7b=840
a+c=120
5a+7b+c=4a+7b+a+c
5a+7b+c=840+120
5a+7b+c=960