一到数学计算题,2.75-｛（负二分之一）-（正六分之五）+（负八分之三）+四又三分之二｝等于多少?

=(2+3/4)-[(-1/2)-(+5/6)+(-3/8)+(4+2/3)]
=2+3/4+1/2+5/6+3/8-4-2/3
=(2-4)+(3/4+3/8)+1/2+(5/6-2/3)
=-2+9/8+1/2+1/6
=-2+1+1/8+1/2+1/6
=-1+(3+12+4)/24
=-1+19/24
=-5/24