a, $\frac{1}{5}$ + $\frac{3}{5}$
= $\frac{1+3}{5}$ = $\frac{4}{5}$
b. $\frac{2}{3}$ . $\frac{2}{7}$ - $\frac{2}{3}$ . $\frac{3}{7}$ + $\frac{8}{7}$ . $\frac{2}{3}$
= $\frac{2}{3}$ . ($\frac{2}{7}$ - $\frac{3}{7}$+ $\frac{8}{7}$)
= $\frac{2}{3}$ . 1 = $\frac{2}{3}$
c. $\frac{-3}{5}$ + $\frac{7}{13}$ + $\frac{-2}{5}$+ $\frac{-23}{25}$ + $\frac{6}{13}$
= ($\frac{-3}{5}$ + $\frac{-2}{5}$) + ($\frac{7}{13}$+ $\frac{6}{13}$)+ $\frac{-23}{25}$
= -1 + 1 + $\frac{-23}{25}$
= 0 + $\frac{-23}{25}$
= $\frac{-23}{25}$
d. (1/3+3/4 -13/12):(12/23+123/234+1234/2345)
= (4/12 + 9/12 - 13/12) : (12/23+123/234+1234/2345)
= 0: (12/23+123/234+1234/2345)
= 0
