Question

se stie ca a+2b+c=51si2a+b+2c=42.Aflati a+b+c

Answer 1

$\left \{ {{a+2b+c=51} \atop {2a+b+2c=42}}\right \ [tex]a+2b+c=51=>a=51-2b-c \\ 2(51-2b-c)+b+2c=42 \\ 102-4b-2c+b+2c=42 \\ 102-3b=42=>-b= \frac{42-102}{3} => \\ => b=20$ight. [/tex]
Inlocuim b in una dintre cele 2 ec.:
$a+2*20+c=51=>a+c=11 \\ a+b+c=11+20=31$