3/2006 + 7/2017 = 3/2006 + (3/2017 + 4/2017) = 3/2006 + 3/2017 + 4/2017
7/2006 + 3/2017 = (3/2006 + 4/2006) + 3/2017 = 3/2006 + 4/2006 + 3/2017
Vì 4/2006 > 4/2017 => 3/2006 + 3/2017 + 4/2017 < 3/2006 + 4/2006 + 3/2017
=> 3/2006 + 7/2017 < 7/2006 + 3/2017