\(6-\frac{2}{5}+\frac{3}{5}\times3\)
\(=\frac{30}{5}-\frac{2}{5}+\frac{9}{5}\)
\(=\frac{30-2+9}{5}\)
\(=\frac{37}{5}\)
\(\left(\frac{31}{35}-\frac{4}{7}\right)\times\frac{8}{7}\div2\)
\(=\left(\frac{31}{35}-\frac{20}{35}\right)\times\frac{8}{14}\)
\(=\frac{11}{35}\times\frac{4}{7}\)
\(=\frac{44}{245}\)