4又5分之2减去2又6分之1减去4分之3
=4+2/5-2-1/6-3/4
=4-2+2/5-1/6-3/4
=2+2/5-(2+9)/12
=2+2/5-11/12
=1+2/5+1-11/12
=1+2/5+1/12
=1+(24+5)/60
=1+29/60
=1又29/60