Tính các biểu thức dưới dây: a) 2/3 + 3/5, b) 7/12 - 2/7 + 1/12, c)12/17 - 5/12 - 4/17

a) \(\frac{2}{3} + \frac{3}{5}\)

= \(\frac{{10}}{{15}} + \frac{9}{{15}}\)

= \(\frac{{19}}{{15}}\)

b) \(\frac{7}{{12}} - \frac{2}{7} + \frac{1}{{12}}\)

= \(\left( {\frac{7}{{12}} + \frac{1}{{12}}} \right) - \frac{2}{7}\)

= \(\frac{2}{3} - \frac{2}{7} = \frac{{14}}{{21}} - \frac{6}{{21}} = \frac{8}{{21}}\)

c) \(\frac{{12}}{{17}} - \frac{5}{{17}} - \frac{4}{{17}}\)

= \(\frac{7}{{17}} - \frac{4}{{17}}\)

= \(\frac{3}{{17}}\)