Tính

Câu hỏi :

Tính :

a) $\frac{3}{4}+\frac{7}{8}=...............................................................$

          b) $\frac{4}{5}-\frac{3}{7}=.......................................................$

          c)$\frac{4}{5}\times \frac{3}{8}=...........................................................$

          d) $\frac{3}{5}: \frac{2}{3}=................................................................$