Đáp án:
`c)9/2-[2/3-(x+7/4)]=-5/4`
`<=>[2/3-(x+7/4)]=9/2-(-5/4)`
`<=>[2/3-(x+7/4)]=9/2+5/4`
`<=>[2/3-(x+7/4)]=18/4+5/4`
`<=>[2/3-(x+7/4)]=23/4`
`<=>2/3-(x+7/4)=23/4`
`<=>(x+7/4)=2/3-23/4`
`<=>(x+7/4)=-61/12`
`<=>x+7/4=-61/12`
`<=>x=-61/12-7/4`
`<=>x=-41/6`
`d)4/3-(x-1/5)=|-3/10+1/2|-1/6`
`<=>4/3-(x-1/5)=|-3/10+5/10|-1/6`
`<=>4/3-(x-1/5)=|2/10|-1/6`
`<=>4/3-(x-1/5)=1/5-1/6`
`<=>4/3-(x-1/5)=1/30`
`<=>(x-1/5)=4/3-1/30`
`<=>(x-1/5)=13/10`
`<=>x-1/5=13/10`
`<=>x=13/10+1/5`
`<=>x=13/10+2/10`
`<=>x=15/10`
Bài `7:`
`a)1/4+|-1/3+7/6|-(-5/12)+1/2`
`=1/4+|-2/6+7/6|+5/12+6/12`
`=1/4+|5/6|+11/12`
`=1/4+5/6+11/12`
`=3/12+10/12+11/12`
`=24/12=2`
`b)|-3/4+1|-1/5+|1/10-3/20|`
`=|-3/4+4/4|-1/5+|2/20-3/20|`
`=|1/4|-1/5+|-1/20|`
`=1/4-1/5+1/20`
`=5/20-4/20+1/20`
`=1/20+1/20`
`=2/20=1/10`
`c)3/4-(12/8+15/3+2/4)-|6/20-7/2|`
`=3/4-(36/24+120/24+12/24)-|6/20-70/20|`
`=3/4-168/24-|-64/20|`
`=3/4-7-64/20`
`=15/20-140/20-64/20`
`=-189/20`
`d)|-6/5+1/2|-(3/4-5/8)+|-3/2|`
`=|-12/10+5/10|-(6/8-5/8)+3/2`
`=|-7/10|-1/8+3/2`
`=7/10-1/8+3/2`
`=28/40-5/40+60/40`
`=83/40`
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