a, 71.2 – 6.(2x+5) =  10 5 : 10 3

71.2 – 6.(2x+5) =  10 2

6.(2x+5) = 71.2 – 100

6.(2x+5) = 42

x = 1

b,  5 x + 3 4 . 6 8 = 6 9 . 3 4

5 x + 3 4 . 6 8 = 6 8 . 6 . 3 4

5 x + 3 4 = 6 8 . 6 . 3 4 : 6 8 = 6 . 3 4

5x =  6 . 3 4 - 3 4 = 5 . 3 4

x =  3 4

c, 12:{390:[5. 10 2  – ( 5 3 + x . 7 2 )]} = 4

390:[5. 10 2  – ( 5 3 + x . 7 2 )] = 12:4 = 3

5. 10 2  – ( 5 3 + x . 7 2 ) = 390:3 = 130

5 3 + x . 7 2 = 5. 10 2  – 130 = 370

x . 7 2 = 370 –  5 3 = 245

x = 245: 7 2 = 5

d,  5 3 .(3x+2):13 =  10 3 : 13 5 : 13 4

5 3 .(3x+2):13 =  10 3 : 13

3x+2 =  10 3 : 13 : 5 3 .13 = 8

x = 2

Lời giải là

92.4−27=a+350a+315

368−27=a+350a+315

341=a+350a+315

a+350a=341−315

a+350a=26

a+350=26.a

26.a−a=350

(26−1).a=350

25.a=350

a=350:25

a=14.

\(92.4-27=\left(x+350\right):x+315\)

\(\Leftrightarrow368-27=\left(x+350\right):x+315\)

\(\Leftrightarrow341=\left(x+350\right):x+315\)

\(\Leftrightarrow\left(x+350\right):x=341-315\)

\(\Leftrightarrow\left(x+350\right):x=26\)

\(\Leftrightarrow\left(x:x\right)+\left(350:x\right)=26\)

\(\Leftrightarrow1+350:x=26\)

\(\Leftrightarrow350:x=26-1\)

\(\Leftrightarrow350:x=25\)

\(\Leftrightarrow x=\dfrac{350}{25}=14\)

Vậy x=14

\(92.4-27=\frac{x+350}{x}+315\)

\(< =>368-27=\frac{x+350}{x}+315\)

\(< =>341=\frac{x+350}{x}+315\)

\(\frac{x+350}{x}=341-315\)

\(\frac{x+350}{x}=26\)

\(\left(x+350\right):x=26\)

\(x+350=x.26\)

\(350=x.25\)

\(x=350:25\)

\(x=14.\)

                                                           Đáp số : 14.

92.4 - 27 = ( x+ 350) / x +315

hay 341 = (x+ 350) / x +315

=> 26 = (x+ 350) / x 

=> 26x = x + 350

=> 25x = 350

=> x= 14

a)720:[41-(2x+5)]=2³.5

720:[41-(2x+5)]=8.5

720:[41-(2x+5)]=40

41-(2x+5)=720:40

41-(2x+5)=18

2x=18-5

2x=13

x=13:2

x=6,5

b)92.4-27=(x+350):x+315

=>(x+350):x+315=92.4-27

(x+350):x+315=368-27

(x+350):x+315=341

 tới đấy mk ko biết làm nữa

\(5^3.\left(3x+2\right):13=10^3:\left(13^5:13^4\right)\\ 125.\left(3x+2\right):13=1000:13\\ 125.\left(3x+2\right)=1000\\ 3x+2=1000:125\\ 3x+2=8\\ 3x=8-2\\ 3x=6\\ x=6:3\\ x=2\)

KUDO SHINICHI:

        Bài làm:

\(92.4-27=x+\frac{350}{x}+315\)

\(368-27=x+\frac{350}{x}+315\)

\(341=\frac{x}{350+315}\Leftrightarrow341=x:350+315\)

\(341=x:665\)

\(x=665.341\)

\(\rightarrow x=226765\)

Vậy x=226765

:3, Chúc bạn học tốt!!

92.4-27=x+350/x +315

368 - 27 = x+350 : x + 315

341 = x : (350 + 315)

341 = x : 665

x = 665 x 341

x = 226765

cam on cac ban