(i) Let the number to be added $$= x$$
$$\therefore \dfrac{5}{12} + x = 2 \dfrac{3}{8}$$
$$\therefore \, Required \,number\, \left(x\right) = 2 \dfrac{3}{8} - \dfrac{5}{12} $$
$$x = \dfrac{19}{8} - \dfrac{5}{12}$$
$$= \dfrac{57 - 10 }{24} = \dfrac{47}{24} = 1\dfrac{23}{24}$$
(ii) Let the number to be subtracted $$= x$$
$$\therefore 5 - x = 1\dfrac{1}{13}$$
Required number $$\left(x\right) = 5 - 1\dfrac{5}{13}$$
$$x = \dfrac{5}{1} - \dfrac{18}{13} $$
$$ = \dfrac{65 - 18}{13} = \dfrac{47}{13} = 3 \dfrac{8}{13}$$