x.8+56+x.4-28=x.3+9+x+4*(1-3)

=>12x+(56-28)=(3x+x)+9+4*(-2)

=>12x+28=4x+9-8=4x+1

=>12x-4x=1-28

8x=-27

x=-27/8

( 3x - 2⁴ ) . 7³ = 2 . 7⁴

3x - 16 = 2 . 7⁴ : 7³ = 14

3x = 14 + 16 = 30

x = 10

\(\left(3\times x-2^4\right)\times7^3=2\times7^4\)

 \(\left(3\times x-2^4\right)\div2=7^4\div7^3\) 

  \(\left(3\times x-16\right)\div2=7\)

           \(3\times x-16=7\times2\) 

           \(3\times x-16=14\) 

                     \(3\times x=14+16\)                      

                      \(3\times x=30\)

                           \(x=30\div3\) 

                           \(x=10\)

x = 10

x+4/7+y = 4/7

=> (x + 4)7 = 4(y + 7)

=> 7x + 28 = 28 + 4y

=> 7x = 4y

=> x/4 = y/7

=> x + y/4 + 7 = x/4 = y/7 mà x + y = 77

=> 77/11 = x/4 = y/7

=> 7 = x/4 = y/7

=> x = 28; y = 49

mk giải được rồi

\(a.\dfrac{1}{4}+\dfrac{3}{4}x=-0,3\)

\(\Leftrightarrow\dfrac{3}{4}x=-\dfrac{11}{20}\)

\(\Leftrightarrow x=-\dfrac{11}{15}\)

\(b.\dfrac{4}{7}x-\dfrac{7}{3}=\dfrac{1}{21}\)

\(\Leftrightarrow\dfrac{4}{7}x=\dfrac{50}{21}\)

\(\Leftrightarrow x=\dfrac{25}{6}\)

a) Ta có:

1; 4; 7;...; 100 có (100 - 1) : 3 + 1 = 34 (số)

1 + 4 + 7+ ... + 100 = (100 + 1) × 34 : 2

= 101 × 17

(1 + 4 + 7 + ... + 100) : a = 17

101 × 17 : a = 17

a = 101 × 17 : 17

a = 100

b) (X - 1/2) × 5/3 = 7/4 - 1/2

(X - 1/2) × 5/3 = 5/4

X - 1/2 = 5/4 : 5/3

X - 1/2 = 3/4

X = 3/4 + 1/2

X = 5/4

a) (1 + 4 + 7 +...+ 100) : a = 17

1717 : a = 17

a = 101

b) \(\left(x-\dfrac{1}{2}\right)\times\dfrac{5}{3}=\dfrac{7}{4}-\dfrac{1}{2}\)

\(\left(x-\dfrac{1}{2}\right)\times\dfrac{5}{3}=\dfrac{10}{8}\)

\(\left(x-\dfrac{1}{2}\right)=\dfrac{10}{8}\div\dfrac{5}{3}\)

\(\left(x-\dfrac{1}{2}\right)=\dfrac{10}{8}\times\dfrac{3}{5}\)

\(\left(x-\dfrac{1}{2}\right)=\dfrac{3}{4}\)

\(x-\dfrac{1}{2}=\dfrac{3}{4}\)

\(x=\dfrac{3}{4}+\dfrac{1}{2}\)

\(x=\dfrac{5}{4}\)

a. (1+4+7+...+100):a=17 

=> ( 100 + 1) x 32 : 2 : a = 17

=> 1717 : a = 17 

=> a = 101

b. \(\left(X-\dfrac{1}{2}\right).\dfrac{5}{3}=\dfrac{7}{4}-\dfrac{2}{4}\)

\(\left(X-\dfrac{1}{2}\right).\dfrac{5}{3}=\dfrac{5}{4}\)

\(X-\dfrac{1}{2}=\dfrac{3}{4}\)

\(X=\dfrac{1}{4}\)

\(x+y=55\Rightarrow x=55-y\\ \Leftrightarrow\dfrac{4+55-y}{7+y}=\dfrac{4}{7}\\ \Leftrightarrow28+385-7y=28+4y\\ \Rightarrow y=35\\ \Rightarrow x=55-35=20\)

Em lắc đầu 

Và lui ra:)))))

giúp

\(\dfrac{x+4}{4}=\dfrac{y+7}{7}\)Theo tc dãy tỉ số bằng nhau 

\(\dfrac{x+4}{4}=\dfrac{y+7}{7}=\dfrac{x+y+4+7}{11}=\dfrac{33}{11}=3\Leftrightarrow x=8;y=14\)

a^2+b^2/b^2+c^2=a/c

\(\dfrac{4}{5}.x=\dfrac{4}{7}\)

\(\Leftrightarrow x=\dfrac{4}{7}\div\dfrac{4}{5}\)

\(\Leftrightarrow x=\dfrac{4}{7}\times\dfrac{5}{4}\)

\(\Leftrightarrow x=\dfrac{5}{7}\)

x=4/7:4/5

x=4/7.5/4

x=5/7(rút gọn)

x=4/7:4/5

x=4/7.5/4

x=5/7

(x-1/2).5/3=7/4-1/2

(x-1/2).5/3=5/4

x-1/2=5/4:5/3

x=3/4+1/2

x=5/4

(x-4/3).7/4=5-7/6

(x+4/3).7/4=23/6

x+4/3=23/6:7/4

x+4/3=46/21

x=46/21-4/3

x=6/7