3+4.4+【(+3又4分之3)+(-8.4)】+(-1又4分之1)+6
=3+4.4+(3.75-8.4)-1.25+6
=3+4.4+3.75-8.4-1.25+6
=(3+6)+(4.4-8.4)+(3.75-1.25)
=9-4+2.5
=5+2.5
=7.5