bài 1 thực hiện phép tính

Bài 1: a) Ta có $\frac{19}{7}+\frac{18}{7}=\frac{19+18}{7}=\frac{37}{7}$. Do đó $\frac{12}{17}+\frac{19}{7}+\frac{18}{7}=\frac{12}{17}+\frac{37}{7}=\frac{12\times 7+37\times 17}{17\times 7}=\frac{84+629}{119}=\frac{713}{119}=6\frac{5}{119}$. b) Ta có $\frac{12}{11}:\frac{1}{3}=\frac{12}{11}\times 3=\frac{36}{11}$. Do đó $\frac{12}{11}:\frac{1}{3}\times \frac{3}{2}=\frac{36}{11}\times \frac{3}{2}=\frac{108}{22}=\frac{54}{11}=4\frac{10}{11}$. c) Ta có $\frac{7}{9}-\frac{2}{3}=\frac{7}{9}-\frac{6}{9}=\frac{1}{9}$. Do đó $\frac{9}{7}\times (\frac{7}{9}-\frac{2}{3})=\frac{9}{7}\times \frac{1}{9}=\frac{9}{63}=\frac{1}{7}$. d) Ta có $\frac{4}{2}+\frac{9}{14}-\frac{3}{7}=\frac{28}{14}+\frac{9}{14}-\frac{6}{14}=\frac{28+9-6}{14}=\frac{31}{14}=2\frac{3}{14}$.