[tex]\frac{a}{\frac{1}{3}}=\frac{b}{3}=\frac{c}{2\frac{6}{9}}=\frac{d}{\frac{7}{3}}\\
\frac{a}{\frac{1}{3}}=\frac{b}{3}=\frac{c}{2\frac{2}{3}}=\frac{d}{\frac{7}{3}}\\
\frac{a}{\frac{1}{3}}=\frac{b}{3}=\frac{c}{\frac{8}{3}}=\frac{d}{\frac{7}{3}}|\cdot\frac{1}{3}\\
\frac{a}{1}=\frac{b}{9}=\frac{c}{8}=\frac{d}{7}\\
a=k;b=9k;c=8k;d=7k\\
a+b+c+d=25\\ k+9k+8k+7k=25 \\
25k=25\\
k=1\\
a=1;b=9;c=8;d=7\\
\overline{abcd}=1987
[/tex]
