Question

daca 2*a+b=5 si 2*b+3*c=7, calculati 4*a+8*b+9*c.

Answer 1

2a+b=5

2b+3c=7

4a+6b+9c =2(2a+b)+3(2b+3c)=  2*5+3*7=  10+21=31
sper sa fie bun

Answer 2

2a+b=5;
2b+3=7;
⇒4a+8b+9c=2[2a+b]+2[2b+3]=2·5+2·7=2[5+7]=2·12=24;