D= ( $\frac{1}{4}$ + $\frac{-5}{13}$ ) + ( $\frac{2}{11}$ + $\frac{-8}{13}$ + $\frac{3}{4}$ )
= $\frac{1}{4}$ + $\frac{-5}{13}$ + $\frac{2}{11}$ + $\frac{-8}{13}$ + $\frac{3}{4}$
= ( $\frac{1}{4}$ + $\frac{3}{4}$ ) + ( $\frac{-5}{13}$ + $\frac{-8}{13}$ ) + $\frac{2}{11}$
= 1 + (-1) + $\frac{2}{11}$
= 0 + $\frac{2}{11}$
= $\frac{2}{11}$