[2又9分之1 +(5.2-2又2分之1)*1又3分之2]/3又2分之1
=[19/9+（5.2-2.5）X5/3]X2/7
=(19/9+2.7X5/3)X2/7
=(19/9+9/2)X2/7
=(38/18+81/18)X2/7
=119/18X2/7
=119/63
=14/9
0.45*1又3分之1-0.25/0.5
=0.45X4/3-1/2
=0.6-0.5
=0.1
=1/10
3.9+3又7分之2+6.1+1又14分之1
=3.9+6.1+23/7+15/14
=10+46/14+15/14
=10+61/14
=14又14分之5
（8分之3*6.75+3又4分之1*8分之3）/1又4分之1
=【3/8X（6+3/4）+13/4X3/8】X4/5
=3/8X（27/4+13/4）X4/5
=10X3/8X4/5
=3