(-2009又6分之5)+(-2008又3分之2)+(-13又2分之1)+(+4020又3分之2)
=(-2010+1/6)+(-2009+1/3)+(-13-1/2)+(4020+2/3)
=(-2010-2009-13+4020)+(1/6+1/3+2/3-1/2)
=-12+2/3
=-11又1/3