[tex]\bf \left( \cfrac{3}{7}-\cfrac{2}{3} \right)+\left( \cfrac{4}{5} \right)\left( \cfrac{2}{3} \right)\implies \stackrel{LCD~21}{\left( \cfrac{3}{7}-\cfrac{2}{3} \right)}+\left( \cfrac{4}{5} \cdot \cfrac{2}{3} \right)[/tex]
[tex]\bf {\left( \cfrac{3\cdot 3-7\cdot 2}{21} \right)}+\left( \cfrac{4\cdot 2}{5\cdot 3} \right)\implies \left( \cfrac{9-14}{21} \right)+\left( \cfrac{8}{15} \right)
\\\\\\
\stackrel{LCD~105}{\cfrac{-5}{21}+\cfrac{8}{15}}\implies \cfrac{-5\cdot 5+8\cdot 7}{105}\implies \cfrac{-25+56}{105}\implies \boxed{\cfrac{31}{105}}[/tex]
