Tính.

a) \(\frac{1}{{15}} + \frac{4}{{15}} = \frac{{1 + 4}}{{15}} = \frac{5}{{15}} = \frac{1}{3}\)

b) \(\frac{{15}}{8} - \frac{3}{8} = \frac{{15 - 3}}{8} = \frac{{12}}{8} = \frac{3}{2}\)

c) \(\frac{7}{{15}} + \frac{4}{5} = \frac{7}{{15}} + \frac{{12}}{{15}} = \frac{{7 + 12}}{{15}} = \frac{{19}}{{15}}\)

d) \(\frac{2}{3} - \frac{3}{8} = \frac{{16}}{{24}} - \frac{9}{{24}} = \frac{{16 - 9}}{{24}} = \frac{7}{{24}}\)