\(\left(\dfrac{242}{363}+\dfrac{1616}{2121}\right)=\dfrac{2}{7}.x\)
\(\Leftrightarrow\dfrac{242}{363}\left(1+\dfrac{8}{7}\right)=\dfrac{2}{7}.x\)
\(\Leftrightarrow\dfrac{242}{363}.\dfrac{15}{7}=\dfrac{2}{7}.x\)
\(\Leftrightarrow\dfrac{10}{7}=\dfrac{2}{7}.x\)
\(\Leftrightarrow x=\dfrac{10}{7}:\dfrac{2}{7}\)
\(\Leftrightarrow x=\dfrac{10}{7}.\dfrac{7}{2}\)
\(\Leftrightarrow x=5\)
=>x*2/7=(2/3+16/21)=14/21+16/21=30/21=10/7
=>x=5