a, \(\dfrac{4x}{7}=\dfrac{1}{5}+\dfrac{2}{3}=\dfrac{3+10}{15}=\dfrac{13}{15}\Rightarrow60x=91\Leftrightarrow x=\dfrac{91}{60}\)

b, \(\dfrac{5}{7}:x=\dfrac{1}{6}+\dfrac{4}{5}=\dfrac{5+24}{30}=\dfrac{29}{30}\Leftrightarrow x=\dfrac{5}{7}:\dfrac{29}{30}=\dfrac{150}{203}\)

\(\left(5.2^2-20\right):\left(5+3^2:6\right)\\ =\left(5.4-20\right):\left(5+9:6\right)\\ =\left(20-20\right):\left(5+\dfrac{3}{2}\right)\\ =1:\dfrac{13}{2}=\dfrac{2}{13}\)

(5*2^2-20):5+3^2/6

=(20-20):5+9/6

=3/2

\(8=2^3\)                 \(12=2^2.3\)                     \(15=3.5\)

\(BCNN\left(8;12;15\right)=2^3.3.5=120\)

\(BC\left(8;12;15\right)=\left\{0;120;240;360;480;....\right\}\)

Biết rằng số học sinh từ \(300< x< 400\)

Vậy số học sinh khối 6 :  \(360em\)

Số học sinh khối 6 bị thừa 5 em học sinh => \(360+5=365em\)

Vậy ....

thx

a) 6/-x=x/-24

=> -x.x=6.-24

=>-x.x=-144

=>x=12 hay x=-12

b)9/x=-35/105

=>9/x=-1/3

=>x=9.3/-1=-27

=>x=-27

c)x-1/8=5/8

=>x=5/8+1/8

=>x=3/4

d)x-1/2-(3/2+x)=-2

=>-x+4/2=-2

=>-x/2=0

=>x=0

e)x+1/3=-12/5.10/6

x+1/3=-4

x=-4-1/3

x= -13/3

#YM

`@` `\text {Ans}`

`\downarrow`

`2+(x+3)=7`

`\Rightarrow x+3=7-2`

`\Rightarrow x+3=5`

`\Rightarrow x=5-3`

`\Rightarrow x=2`

`5+(3+x)=10`

`\Rightarrow 3+x=10-5`

`\Rightarrow 3+x=5`

`\Rightarrow x=5-3`

`\Rightarrow x=2`

`(4+x)+1=7`

`\Rightarrow 4+x=7-1`

`\Rightarrow 4+x=6`

`\Rightarrow x=6-4`

`\Rightarrow x=2`

`(x+5)+3=9`

`\Rightarrow x+5=9-3`

`\Rightarrow x+5=6`

`\Rightarrow x=6-5`

`\Rightarrow x=1`

`(x-1)-4=7`

`\Rightarrow x-1=7+4`

`\Rightarrow x-1=11`

`\Rightarrow x=11+1`

`\Rightarrow x=12`

`4-(6-x)=1`

`\Rightarrow 6-x=4-1`

`\Rightarrow 6-x=3`

`\Rightarrow x=6-3`

`\Rightarrow x=3`

\(2+\left(x+3\right)=7\)

\(\Rightarrow2+x+3=7\)

\(\Rightarrow x+5=7\)

\(\Rightarrow x=2\)

\(5+\left(3+x\right)=10\)

\(\Rightarrow5+3+x=10\)

\(\Rightarrow x+8=10\)

\(\Rightarrow x=2\)

\(\left(4+x\right)+1=7\)

\(\Rightarrow4+x+1=7\)

\(\Rightarrow x+5=7\)

\(\Rightarrow x=2\)

\(\left(x+5\right)+3=9\)

\(=x+5+3=9\)

\(\Rightarrow x+8=9\)

\(\Rightarrow x=1\)

\(\left(x-1\right)-4=7\)

\(\Rightarrow x-1-4=7\)

\(\Rightarrow x-5=7\)

\(\Rightarrow x=12\)

\(4-\left(6-x\right)=1\)

\(\Rightarrow4-6-x=1\)

\(\Rightarrow-2-x=1\)

\(\Rightarrow x=-3\)

KHO THE

\(A=\frac{\left[\left(25-1\right):1+1\right]\left(25+1\right)}{2}=325.\)

\(B=\frac{\left[\left(51-3\right):2+1\right]\left(51+3\right)}{2}=675\)

\(C=\frac{\left[\left(81-1\right):4+1\right]\left(81+1\right)}{2}=861\)

mình câng gấp ạ

cần

\(\left(0,75-\frac{1}{4}\right):\frac{5}{6}=\left(\frac{3}{4}-\frac{1}{4}\right):\frac{5}{6}\)

\(=\frac{1}{2}:\frac{5}{6}=\frac{3}{5}\)

C1:(0,75-1/4):5/6

=(3/4-1/4):5/6

=1/2:5/6

=3/5

C2:(0,75-1/4):5/6

=(0,75-0,25). 6/5

=0,5.1,2

= 0.6