(5又4/15-(0.25+1/3)*7.2)/2又2/5
=(5又4/15-0.25*7.2-1/3*7.2)/2又2/5
=(5又4/15-1.8-2.4)/2又2/5
=(5又4/15-4又3/15)/12/5
=16/15×5/12
=4/9
(5又4/15-(0.25+1/3)*7.2)/2又2/5
=(5又4/15-0.25*7.2-1/3*7.2)/2又2/5
=(5又4/15-1.8-2.4)/2又2/5
=(5又4/15-4又3/15)/12/5
=16/15×5/12
=4/9