460 + 85 *4 = x + 175 / 5 + 30

460 + 340 = x + 35 + 30

800 = x + 65

x = 800 - 65

x = 735

 460 +  85 *4 = x + 175 :5 +  30    

    460 + 340  = x + 35 + 30

           800     = x + 65

            x         = 800 - 65 = 735

460+85*4=x+\(\frac{175}{5}\)+30

460+340=x+35+30

800=x+65

x=800-65=735

\(460+85\) x \(4=\frac{x+175}{5}+30\)

 \(460+340=\frac{x+175}{5}+30\)

\(800=\frac{x+175}{5}+30\\ \frac{x+175}{5}=800-30\\ \frac{x+175}{5}=770\)

\(x+175=770\) x \(5\)

\(x+175=3850\\ x=3850-175\\ x=3675\)

460 - 80 x 4 = ( x + 200) : 4
460 - 340 = (x + 200) : 4
120 = ( x + 200) : 4
x + 200 = 120 x 4
x + 200 = 480
          x = 480 - 200
          x = 280

=23 x (58-30) + 28 x 77

=23 x 28 +28 x 77

=28 x (23+77)

=28 x 100

=2800

học tốt bạn nhé

bài này là dạng nâng cao về toán tính nhanh, mik nghĩ là ẽ ít bạn trả lời đc 

bằng 2800

2a

4c

6d

7c

8c

----------------

1 drove->drive

4 will ride->is riding

`48/[x+4]+48/[x-4]=5`           `ĐK: x \ne +-4`

`<=>[48(x-4)+48(x+4)]/[(x-4)(x+4)]=[5(x+4)(x-4)]/[(x-4)(x+4)]`

   `=>48x-192+48x+192=5x^2-80`

`<=>5x^2-96x-80=0`

`<=>5x^2-100+4x-80=0`

`<=>5x(x-20)+4(x-20)=0`

`<=>(x-20)(5x+4)=0`

`<=>` $\left[\begin{matrix} x=20\\ x=\dfrac{-4}{5}\end{matrix}\right.$   (t/m)

Vậy `S={-4/5;20}`

ĐK : \(x\ne\pm4\)

\(\Leftrightarrow\cdot\dfrac{48\left(x+4\right)+48\left(x-4\right)}{\left(x+4\right)\left(x-4\right)}=\dfrac{5\left(x+4\right)\left(x-4\right)}{\left(x+4\right)\left(x-4\right)}\)

\(\Leftrightarrow48x+192+48x-192==5x^2-80\)

\(\Leftrightarrow96x=5x^2-80\)

\(\Leftrightarrow5x^2-96x-80=0\)

\(\Leftrightarrow5x^2+4x-100-80=0\)

\(\Leftrightarrow4\left(x-20\right)+5x\left(x-20\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-20=0\\5x=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=20\\x=-\dfrac{4}{5}\end{matrix}\right.\)

khó quá ??????????????????????????????????

a) (-2) . ( x+7 ) + (-5) = 7 

<=>(-2).(x+7)=7+5

<=>x+7=12:(-2)

<=>x+7=-6

<=>x=(-6)-7

<=>x=-13

Vậy x=-13

b)(x+4) : (-7) = 14

<=>x+4=14 x (-7)

<=>x+4=-98

<=>x=-98-4

<=>x=-102

Vậy x= -102

c) 72 : ( x+5) - 4 = -12 

<=>72:(x+5)=(-12)+4

<=>x+5=72:(-8)

<=>x+5=-9

<=>x=-9-5

<=>x=-14

Vậy x= -14

d) (x+3) : (-6 ) + 12 = 8 

<=>(x+3) :(-6)=8-12

<=>x+3=(-4)x(-6)

<=>x+3=24

<=>x=24-3

<=>x=21

Vậy x= 21 

\(21_{10}=10101_2\)

\(0,18\text{×}1230+0,9\text{×}1567\text{×}2-3\text{×}690\\ =221,4+2820,6-2070=1015\)