①.-2分之5的绝对值-(-3.5)+-1-2分之3的绝对值
=|-5/2|-(-3.5)+-1-|3/2|
=5/2+7/2-1-3/2
=9/2-1
=7/2
②(-0.125)+(-0.75)+(-4分之3)+8分之1+1
=-0.125-0.75-3/4+1/8+1
=-0.125-0.75-0.75+0.125+1
=-1.5+1
=-0.5
③根据下列条件求a-b+c-b的值.
（1）a=-18,b=-12,c=6,d=5
a-b+c-b
=(-18)-(-12)+6-5
=-18+12+6-5
=-5
（2）a=-3分之1,b=4分之3,c=-2分之1,d=12分之5
a-b+c-b
=(-1/3)-(3/4)+(-1/2)-5/12
=-1/3-3/4-1/2-5/12
=-4/12-9/12-6/12-5/12
=-24/12
=-2
④（4又8分之7）减(5又2分之1）加（负4又4分之1）减（3又8分之1）
=(4+7/8)-(5+1/2)+(-4-1/4)-(3+1/8)
=4+7/8-5-1/2-4-1/4-3-1/8
=4-5-4-3+7/8-1/2-1/4-1/8
=-8+7/8-4/8-2/8-1/8
=-8