Tính:
a) \(\displaystyle {4 \over 7} + {3 \over 7}\) b) \(\displaystyle {3 \over 8} + {3 \over 4}\)
c) \(\displaystyle {1 \over 6} - {1 \over {12}}\) d) \(\displaystyle {{13} \over 7} - {9 \over 5}\)
a) \(\displaystyle {4 \over 7} + {3 \over 7} = {7 \over 7} = 1\)
b) \(\displaystyle {3 \over 8} + {3 \over 4} = {{3} \over 8} + \dfrac{6}{8}= {9 \over 8}\)
c) \(\displaystyle {1 \over 6} - {1 \over {12}} = \dfrac{2}{12}-{{1} \over {12}} = {1 \over {12}}\)
d) \(\displaystyle {{13} \over 7} - {9 \over 5} = {{65 } \over {35}} - \dfrac{63}{35} = {2 \over {35}}\)
-- Mod Toán lớp 4