The formula of a midpoint between E and F:
[tex]M_{EF}\left(\dfrac{x_E+x_F}{2};\ \dfrac{y_E+y_F}{2}\right)[/tex]
We have the points [tex]\left(\dfrac{3}{5},\ -\dfrac{6}{7}\right)[/tex] and [tex]\left(\dfrac{2}{5},\ \dfrac{5}{7}\right)[/tex]. Substitute:
[tex]\dfrac{\frac{3}{5}+\frac{2}{5}}{2}=\dfrac{\frac{5}{5}}{2}=\dfrac{1}{2}\\\\\dfrac{-\frac{6}{7}+\frac{5}{7}}{2}=\dfrac{-\frac{1}{7}}{2}=-\dfrac{1}{7}\cdot\dfrac{1}{2}=-\dfrac{1}{14}[/tex]
Answer: [tex]\boxed{\left(\dfrac{1}{2},\ -\dfrac{1}{14}\right)}[/tex]