Răspuns:
60
Explicație pas cu pas:
3a+6b=42 |:3, ⇒a+2b=14
3b+5a+c=32
7(a+b)+c=???
7(a+b)+c=7a+7b+c=5a+3b+c+2a+4b=32+2·(a+2b)=32+2·14=32+28=60
3a+6b=42 I :3
a+2b=14
3b+5a+c+2(a+2b)=32+2·14
3b+5a+c+2a+4b=60=> 7a+7b+c=60=>7(a+b)+c=60
