$$\left. \begin{array} { l } { D + D = 13 } \\ { \frac { E } { 13 } - \frac { D } { 13 } = 6 } \end{array} \right.$$
$D = \frac{13}{2} = 6\frac{1}{2} = 6.5$
$E = \frac{169}{2} = 84\frac{1}{2} = 84.5$
