Rút gọn rồi tính:

Lời giải:

\[\frac{6}{{35}} + \frac{{36}}{{63}} = \frac{6}{{35}} + \frac{4}{7} = \frac{6}{{35}} + \frac{{20}}{{35}} = \frac{{26}}{{35}}\]

\[\frac{3}{{24}} + \frac{{20}}{{64}} = \frac{1}{8} + \frac{5}{{16}} = \frac{2}{{16}} + \frac{5}{{16}} = \frac{7}{{16}}\]

\[\frac{{40}}{{72}} + \frac{8}{{27}} = \frac{5}{9} + \frac{8}{{27}} = \frac{{15}}{{27}} + \frac{8}{{27}} = \frac{{23}}{{27}}\]