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Bài 2

1) 
$2 + \frac{3}{4} = \frac{8}{4} + \frac{3}{4} = \frac{8+3}{4} = \frac{11}{4}$
2) 
$\frac{5}{3} - 1 = \frac{5}{3} - \frac{3}{3} = \frac{5-3}{3} = \frac{2}{3}$
3) 
$-1 + \frac{1}{5} = -\frac{5}{5} + \frac{1}{5} = \frac{-5+1}{5} = -\frac{4}{5}$
4) 
$-1 - \frac{6}{5} = -\frac{5}{5} - \frac{6}{5} = \frac{-5-6}{5} = -\frac{11}{5}$
5) 
$-3 + \frac{-3}{7} = -3 - \frac{3}{7} = -\frac{21}{7} - \frac{3}{7} = \frac{-21-3}{7} = -\frac{24}{7}$
6)
$-\frac{6}{7} - 2 = -\frac{6}{7} - \frac{14}{7} = \frac{-6-14}{7} = -\frac{20}{7}$