Tính rồi rút gọn:

\(\frac{5}{{14}}\) +\(\frac{3}{{14}}\) = \(\frac{{5 + 3}}{{14}}\)= \(\frac{8}{{14}}\)= \(\frac{4}{7}\)

\(\frac{{31}}{{28}}\) - \[\frac{{11}}{{28}}\] = \(\frac{{31 - 11}}{{28}}\)= \(\frac{{20}}{{28}}\)= \(\frac{5}{7}\)

\[\frac{{10}}{{21}}\]  + \(\frac{8}{{21}}\) = \(\frac{{10 + 8}}{{21}}\)= \(\frac{{18}}{{21}}\)= \(\frac{6}{7}\) 

\(\frac{{35}}{{36}}\) - \(\frac{{17}}{{36}}\) = \(\frac{{35 - 17}}{{36}}\)= \(\frac{{18}}{{36}}\)= \(\frac{1}{2}\)