Đáp án:
`A=0`
`B=89/27`
`C=(-3)/2`
Giải thích các bước giải:
`A=1/2-3/4+5/6-7/12`
`=6/12-9/12+10/12-7/12`
`=(6-9+10-7)/12`
`=0/12`
`=0`
`B=-3-2/3 .((-10)/9-25/3)`
`=-3-2/3 .((-10)/9-75/9)`
`=-3-2/3 . (-85)/9`
`=-3+170/27`
`=-81/27+170/27`
`=89/27`
`C=(12/35-6/7+18/14):6/(-7)-(-2)/5-1`
`=(12/35-6/7+9/7) . (-7)/6+2/5-1`
`=(12/35+3/7). (-7)/6+2/5-1`
`=(12/35+15/35). (-7)/6+2/5-1`
`=27/35 . (-7)/6+2/5-1`
`=(-9)/10+2/5-1`
`=(-9)/10+4/10-10/10`
`=(-15)/10`
`=(-3)/2`
