a,\(x;\dfrac{7}{11}=\dfrac{4}{7}+\dfrac{1}{14}\)
\(x:\dfrac{7}{11}=\dfrac{8}{14}+\dfrac{1}{14}=\dfrac{9}{14}\)
\(x=\dfrac{9}{14}.\dfrac{7}{11}\)
\(x=\dfrac{63}{154}=\dfrac{9}{22}\)
\(b,\dfrac{9}{7}.x+\dfrac{5}{7}.x=\dfrac{2}{3}\)
\(\left(\dfrac{9}{7}+\dfrac{5}{7}\right).x=\dfrac{2}{3}\)
\(2x=\dfrac{2}{3}\)
\(x=\dfrac{2}{3}:2\)
\(x=\dfrac{2}{3}.\dfrac{1}{2}=\dfrac{1}{3}\)