2|3A+4|+|4B+3|=-|C+1|,
∴3A+4=0,4B+3=0,C+1=0,
∴A=-4/3,B=-3/4,C=-1.
A-B+C的相反数=-(A-B+C)
=-(-4/3+3/4-1)
=-(-19/12)
=19/12.