Răspuns :
[tex]4a+3x+4b=66\\
4(a+b)+3x=66\\
4*6+3x=66\\
24+3x=66\\
3x=42\\
x=42:3\\
x=14\\\\
Proba:4*6+14*3=66\\
24+42=66\\
66=66[/tex]
[tex]a+b=6 \\ 4*a+3*x+4*b=66=\ \textgreater \ 4(a+b)+3*x=66=\ \textgreater \ \\ 4*6+3*x=66=\ \textgreater \ 3*x=66-24=42=\ \textgreater \ x= \frac{42}{3} =14 \\BlackBook[/tex]