C. % A = 35%; % T =35% ; %G = 15%; X = 15%

a

\(\left(-35\right):63=-15:x\\ \dfrac{-35}{63}=\dfrac{-15}{x}\\ x=\dfrac{-15.63}{-35}=\dfrac{3.\left(-5\right).7.9}{-35}=\dfrac{3.\left(-35\right).9}{-35}=3.9=27\)

(-35) : 63 = -15 : \(x\)

\(x\) = (-15) : [ (-35) : 63]

\(x\) = -15 x \(\dfrac{63}{-35}\)

\(x\) = 27

(- 35) : 63 = - 15 : x

- 35/ 63 = - 15/ x

- 5/ 9 = - 15/ x

- 15/ 27 = - 15/ x

=> x = 27

`@` `\text {Ans}`

`\downarrow`

`18*15 + 35 + 15*32 + 35*49`

`= 15 (18+32) + 35(1+49)`

`= 15*50 + 35*50`

`= 50*(15+35)`

`= 50*50`

`= 2500`

=15*50+35*50

=50*50

=2500

\(18.15+35+15.32+35.49\)

\(=18.15+35.1+15.32+35.49\)

\(=\left(15+35\right).\left(18+32+49+1\right)\)

\(=50.100\)

\(=5000\)

a)(x-15)=0     

x=15

Vậy c=15

b)(x-10)=1

x=11

Vậy x=11

c)(x-5)(x-7)=0

x=5 hoặc x=7

Vậy \(x\in\left\{5;7\right\}\)

\(18.15+35+15.32+35.4+9\)

\(=\left(18.15+15.32\right)+\left(35+35.4\right)+9\)

\(=\left[15.\left(18+32\right)\right]+\left[35.\left(1+4\right)\right]+9\)

\(=\left[15.50\right]+\left[35.5\right]+9\)

\(=750+175+9\)

\(=934\)

= 454.46875

\(18.15+35+15.32+35.4+9\)

\(=15.\left(18+32\right)+35.\left(1+4\right)+9\)

\(=15.50+35.5+9\)

\(=15.50+\left(15+20\right).5+9\)

\(=15.50+15.5+20.5+9\)

\(=15.\left(50+5\right)+100+9\)

\(=15.55+109\)

\(=825+109=934\)

a, x=15
b, x=11
c, x=7
d, x=36

Bài 6:

a)(x-15).15=0

⇔x-15=0

⇔x=15

b)32(x-10)=32

⇔x-10=1

⇔x=11

c)(x-5)(x-7)=0

⇔x-5=0 hay x-7=0

⇔x=5 hay x=7

d)(x-35)35=35

⇔x-35=1

⇔x=36

a, x = 15
b, x = 11
c, x = 7 hoặc x = 5
d, x = 36

A.\(\left(x-15\right).15=0\)

\(x-15=0:15\)

\(x-15=0\)

\(x=15+0\)

\(x=15\)

B.\(32\left(x-10\right)=32\)

\(x-10=32:32\)

\(x-10=1\)

\(x=10+1\)

\(x=11\)

`a) `

`(x-15)xx15=0`

`<=> x-15 = 0 : 15`

`<=> x-15 = 0`

`<=> x = 0 + 15`

`<=> x =15`

`b)`

`32.(x-10)=32`

`<=> x - 10 = 32:32`

`<=>x-10=1`

`<=> x = 1+10`

`<=> x =11`

`c)`

`(x-5).(x-7)=0`

`<=>` \(\left[ \begin{array}{l}x-5 = 0\\x-7=0\end{array} \right.\) 

`<=>` \(\left[ \begin{array}{l}x=5\\x=7\end{array} \right.\) 

`d)`

`(x-35)xx35=35`

`<=> x - 35 = 35:35`

`<=> x - 35 = 1`

`<=> x = 1+35`

`<=> x = 36`

(75+35+15)-(15-75+35)

=  75 + 35 + 15 - 15 + 75 - 35

= (35 - 35) + (15 - 15) + (75 + 75)

= 0 + 0 + 150

= 150

= 75+35+15-15+75-35

=(75+75) + ( 35-35)+ (15-15)

= 150+0+0=150