Đề bài

Bỏ dấu ngoặc rồi tính:

a)$\left( {\frac{{ - 3}}{7}} \right) + \left( {\frac{5}{6} - \frac{4}{7}} \right);$                          

b)$\frac{3}{5} - \left( {\frac{2}{3} + \frac{1}{5}} \right);$

c)$\left[ {\left( {\frac{{ - 1}}{3} + 1} \right) - \left( {\frac{2}{3} - \frac{1}{5}} \right)} \right];$                  

d)$1\frac{1}{3} + \left( {\frac{2}{3} - \frac{3}{4}} \right) - \left( {0,8 + 1\frac{1}{5}} \right)$.