0.75+(-2又4分之3)+0.125+12又7分之5+(-4又8分之1)
=3/4+(-2-3/4)+1/8+12+5/7+(-4-1/8)
=3/4-2-3/4+1/8+12+5/7-4-1/8
=3/4-3/4+1/8-1/8+12-4-2+5/7
=6+5/7
=6又5/7