\(16:\left(\frac{\frac{3}{5}.x+8}{21}+9\right)=\frac{7}{10}\)
\(16:\left(\frac{\frac{3}{5}.x+8}{21}+\frac{189}{21}\right)=\frac{7}{10}\)
\(16:\left(\frac{\frac{3}{5}.x+197}{21}\right)=\frac{7}{10}\)
\(\frac{\frac{3}{5}x+197}{21}=\frac{160}{7}\)
\(7.\left(\frac{3}{5}x+197\right)=3360\)
\(\frac{21}{5}x+1379=3360\)
\(\frac{21}{5}x=1981\)
\(x=\frac{1415}{3}\)