2.1-11/12+5/12=2又1/10-(11/12-5/12)=2又1/10-1/2=2又1/10-5/10=1又3/5
red
2.1-11/12+5/12=2.1-(11/12-5/12)=2.1-1/2=2.1-0.5=1.6