(45.75)*2又九分之五+(-35.25)*(-2又九分之五)+10.5*(—七又九分之四)
=(45.75)*2又九分之五+35.25*(2又九分之五)+10.5*(20-2又九分之五)
=(45.75)*2又九分之五+35.25*(2又九分之五)+210-10.5* 2又九分之五
=(45.75+35.25-10.5)*2又九分之五+210
=70.5*(2+5/9)+210
=141+70.5*5/9+210
=351+(72-1.5)*5/9
=351+40-7.5/9
=391-5/6
=390又1/6