Điền vào chỗ chấm. 2/9 + 5/9 =

a) \[\frac{2}{9} + \frac{5}{9} = \frac{7}{9}\]

b) \[\frac{{13}}{{27}} + \frac{{11}}{{27}} = \frac{{24}}{{27}}\]

c) \[\frac{{36}}{{79}} + \frac{{23}}{{79}} = \frac{{59}}{{79}}\]

d) \[\frac{1}{{11}} + \frac{3}{{11}} = \frac{4}{{11}}\]