2又五分之二×(5/6+3/4)-1/12
=12/5×5/6+12/5×3/4-1/12
=2+9/5-1/12
=2+103/60
=223/60 2又五分之四×(5/6+3/4)-1/12=14/5×5/6+14/5×3/4-1/12=7/3+21/10-1/12=21/10+28/12-1/12=2.1+27/12=2.1+9/4=2.1+2.25=4.35