a, `(7+7/5-2/3)-(4+4/5+3/8)+(3-3/5+2/3+3/8)`
`=7+7/5-2/3-4-4/5-3/8+3-3/5+2/3+3/8`
`=(7-4+3)+(7/5-4/5-3/5)+(2/3-2/3)+(3/8-3/8)`
`=6+0+0+0=6`
b) ý này chưa chụp hết đề
c, `1/3-3/4+3/5+1/2007-1/36+1/15-2/9`
`=(1/3+3/5+1/15)-(3/4+2/9+1/36)+1/2007`
`=(5/15+9/15+1/15)-(27/36+8/36+1/36)+1/2007`
`=1-1+1/2007=1/2007`
d, `1/1.2+1/2.3+1/3.4+...+1/2006.2007`
`=1-1/2+1/2-1/3+1/3-1/4+...+1/2006-1/2007`
`=1-1/2007=2006/2007`
