13/17 + (-3.5)+(-6)]+[+2.5)+(+6)+(4/17)]
=13/17 + (-3.5) + ( -6) + ( +2.5) + ( +6 ) + 4/17
=(13/17+4/17)+[( -3.5) + ( +2.5)] + [( -6 ) + ( +6 )]
=1 - 1 + 0
=0