Đáp án + Giải thích các bước giải:
Cách `1` :
`A=(1/2-2+2/3)-(7+1/2-2/3)-(1/2-2/3-5)`
`=(3/6-12/6+4/6)-(42/6+3/6-4/6)-(3/6-4/6-30/6)`
`=-5/6-41/6-(-31/6)`
`=-5/6-41/6+31/6`
`=-15/6 = -5/2`
Cách `2` :
`A=(1/2-2+2/3)-(7+1/2-2/3)-(1/2-2/3-5)`
`=1/2-2+2/3-7-1/2+2/3-1/2+2/3+5`
`=(1/2-1/2-1/2)+(-2-7+5)+(2/3+2/3+2/3)`
`=-1/2-4+2`
`=-1/2-2`
`=-1/2-4/2=-5/2`.