解：∵?$|a-\frac {1}{2}|+|b+\frac {1}{3}|+|c-\frac {1}{4}|=0$?，且?$|a-\frac {1}{2}|≥0$?、?$|b+\frac {1}{3}|≥0$?、?$|c-\frac {1}{4}|≥0$?
∴?$|a-\frac {1}{2}|=0$?，?$|b+\frac {1}{3}|=0$?，?$|c-\frac {1}{4}|=0$?
得?$a=\frac {1}{2}$?，?$b=-\frac {1}{3}$?，?$c=\frac {1}{4}$?
則?$b-a+c=-\frac {1}{3}-\frac {1}{2}+\frac {1}{4}=-\frac {7}{12}$?
