[tex]\displaystyle\\
a;~b;~c~~ \text{direct proportionale cu:}~~ 4;~6;~9\\\\
\frac{a}{4} =\frac{b}{6} =\frac{c}{9} =k\\\\
a=4k\\
b=6k\\
c=9k\\\\
a+b+c = 76\\
4k+6k+9k=76\\
19k=76\\\\
k= \frac{76}{19} =\boxed{4}\\\\
a=4k=4\times4=\boxed{16}\\
b=6k=6\times4=\boxed{24}\\
c=9k=9\times4=\boxed{36}\\\\
\text{Verificare: }~~ 16+24+36 = 40+36=76~~~OK
[/tex]