Trân xaugai=]

=> sao con nói dịi ;-; 

:)))

`3)`

\(a,\dfrac{1}{3}-\dfrac{2}{3}x=-2,5\\ =>\dfrac{1}{3}-\dfrac{2}{3}x=-\dfrac{25}{10}\\ =>\dfrac{1}{3}-\dfrac{2}{3}x=-\dfrac{5}{2}\\ =>\dfrac{2}{3}x=\dfrac{1}{3}-\left(-\dfrac{5}{2}\right)\\ =>\dfrac{2}{3}x=\dfrac{1}{3}+\dfrac{5}{2}\\ =>\dfrac{2}{3}x=\dfrac{2}{6}+\dfrac{15}{6}\\ =>\dfrac{2}{3}x=\dfrac{17}{6}\\ =>x=\dfrac{17}{6}:\dfrac{2}{3}\\ =>x=\dfrac{17.2}{6.3}\\ =>x=\dfrac{17.1}{2.3}\\ =>x=\dfrac{17}{6}\\ b,30\%x-0,5=-2,75\\ =>0,3x-0,5=-2,75\\ =>0,3x=-2,75+0,5\\ =>0,3x=-2,25\\ =>x=-2,25:0,3\\ =>x=-7,5\)

`4)`

\(a,\dfrac{2x+1}{12}=\dfrac{1}{-4}\\ =>2x+1:12=-\dfrac{1}{4}\\ =>2x+1=-\dfrac{1}{4}.12\\ =>2x+1=-\dfrac{12}{4}\\ =>2x+1=-3\\ =>2x=-3-1\\ =>2x=-4\\ =>x=-4:2\\ =>x=-2\\ b,\left(2\dfrac{1}{5}+\dfrac{3}{5}x\right):\dfrac{1}{3}=\dfrac{3}{4}\\ =>\dfrac{11}{5}+\dfrac{3}{5}x=\dfrac{3}{4}.\dfrac{1}{3}\\ =>\dfrac{11}{5}+\dfrac{3}{5}x=\dfrac{1}{4}\\ =>\dfrac{3}{5}x=\dfrac{1}{4}-\dfrac{11}{5}\\ =>\dfrac{3}{5}x=\dfrac{5}{20}-\dfrac{44}{20}\\ =>\dfrac{3}{5}x=-\dfrac{29}{20}\\ =>x=-\dfrac{29}{20}:\dfrac{3}{5}\\ =>x=-\dfrac{29}{20}.\dfrac{5}{3}\\ =>x=-\dfrac{29.5}{20.3}\\ =>x=-\dfrac{29.1}{4.3}\\ =>x=-\dfrac{29}{12}\)

`2/3 . 1/7 + 2/3 . 6/7 - 1/3 `

`= 2/3 ( 1/7 + 6/7 ) - 1/3`

`= 2/3 . 1 - 1/3`

`= 2/3 - 1/3`

`=1/3`

2

1

`1/3+3/4+2/3+1/4`

`=(1/3+2/3)+(3/4+1/4)`

`=3/3+4/4`

`=1+1`

`=2`

`y:0,25+yxx96=3200`

`=>y xx 4 + y xx 96 = 3200`

`=>y xx ( 4 + 96 ) = 3200`

`=>y xx 100 = 3200`

`=>y = 3200:100`

`=>y=32`