\(=\left(\frac{3}{5}+\frac{2}{5}\right)+\left(\frac{6}{11}+\frac{16}{11}\right)+\left(\frac{7}{13}+\frac{19}{13}\right)\)
\(=1+2+2\)
\(=5\)
\(\frac{3}{5}\) + \(\frac{6}{11}\) + \(\frac{7}{13}\) + \(\frac{2}{5}\) + \(\frac{16}{11}\) + \(\frac{19}{13}\)
= ( \(\frac{3}{5}\)+ \(\frac{2}{5}\) ) + ( \(\frac{6}{11}\)+ \(\frac{16}{11}\) ) + ( \(\frac{7}{13}\) + \(\frac{19}{13}\) )
= 1 + 2 + 2
= 5
\(\Leftrightarrow\)(6/11+16/11) + (3/5 +2/5) + (7/13 +19/13) = 22/11 +1 +26/13
=2+ 1 +2 =5
(Dự vào tính chất giao hoán kết hợp ấy nha)