[tex]a+b+c=783 \\ a:b=2 \ rest \ 9 \to a=2b+9 \\c=2*a \\ \\ 2b+9+b+2(2b+9)=783 \\ 2b+9+b+4b+18=783 \\7b+27=783 \\ 7b=783-27 \\ 7b=756 |:7\\ \boxed{b=108} \\ \\ \boxed{a=2*108+9=225 }\\ \\\boxed{ c=2*225=450} \\ \\ \\ \boxed{\boxed{Verificare : a+b+c= 225+108+450=783 (Adevarat )}}[/tex]