Add the following rational numbers :

(i) $\dfrac{5}{11}$ and $\dfrac{4}{11}$

(ii) $\dfrac{-3}{8}$ and $\dfrac{5}{8}$

(iii) $\dfrac{-6}{13}$ and $\dfrac{8}{13}$

(iv) $\dfrac{-8}{15}$ and $\dfrac{-7}{15}$

(v) $\dfrac{-13}{20}$ and $\dfrac{17}{20}$

(vi) $\dfrac{-3}{8}$ and $\dfrac{5}{-8}$

(i) $\dfrac{5}{11}$ and $\dfrac{4}{11}$

We have:

$\dfrac{5}{11} + \dfrac{4}{11} = \dfrac{5 + 4}{11} = \dfrac{9}{11}$

Hence, the answer is $\dfrac{9}{11}$

(ii) $\dfrac{-3}{8}$ and $\dfrac{5}{8}$

We have:

$\dfrac{-3}{8} + \dfrac{5}{8} = \dfrac{-3 + 5}{8} = \dfrac{2}{8}$

Hence, the answer is $\dfrac{2}{8}$

(iii) $\dfrac{-6}{13}$ and $\dfrac{8}{13}$

We have:

$\dfrac{-6}{13} + \dfrac{8}{13} = \dfrac{-6 + 8}{13} = \dfrac{2}{13}$

Hence, the answer is $\dfrac{2}{13}$

(iv) $\dfrac{-8}{15}$ and $\dfrac{-7}{15}$

We have:

$\dfrac{-8}{15} + \dfrac{-7}{15} = \dfrac{(-8) + (-7)}{15} = \dfrac{-15}{15}$

Hence, the answer is $\dfrac{-15}{15}$

(v) $\dfrac{-13}{20}$ and $\dfrac{17}{20}$

We have:

$\dfrac{-13}{20} + \dfrac{17}{20} = \dfrac{-13 + 17}{20} = \dfrac{4}{20}$

Hence, the answer is $\dfrac{4}{20}$

(vi) $\dfrac{-3}{8}$ and $\dfrac{5}{-8}$

First, express $\dfrac{5}{-8}$ with a positive denominator:

$\dfrac{5}{-8} = \dfrac{5 \times (-1)}{-8 \times (-1)} = \dfrac{-5}{8}$

Now, add the numbers:

$\dfrac{-3}{8} + \dfrac{-5}{8} = \dfrac{(-3) + (-5)}{8} = \dfrac{-8}{8}$

Hence, the answer is $\dfrac{-8}{8}$