a) 159 - (25 - x) = 43

25 - x = 159 - 43

25 - x = 116

x = 25 - 116

x = -91

b) (x - 15) : 4 = 5² - 2³

(x - 15) : 4 = 25 - 8

(x - 15) : 4 = 17

x - 15 = 17 . 4

x - 15 = 68

x = 68 + 15

x = 83

1.Tính 

a) 7.[ 6 : 2 - 15 :(-3) - l-3l ]

=  7.[ 3 + 5 - 3]

=  7.[( 3 - 3 ) + 5]

=  7.[0 + 5]

=  7.5

=  35

b) 159.(18-59) - 59 .(18-159)

= 159 . ( - 41) - 59 . ( - 141 )

= ( - 6519 ) - ( - 8319 )

= 1800

2.Tìm x thuộc Z

a) x + 15 = 20 -4x

    x+4x=20-15

    5x=5

      x=5:5

      x=1

Vậy x=1

b) 3 - lx - 1l =0

    |x-1|=3

* x-1=3            * x-1=-3

      x=3+1             x=-3+1

      x=4                 x=-2

Vậy x=4 hoặc x=-2

c) 7(x-3) - 5 (3-x) = 11x - 5

    7x-21-15+5x=11x-5

    -21-15+5=11x-7x-5x

    -31=-x

     31=x

Vậy x=31  

a,   x/12=10

    x=10*12=120

b. 159/n=3

n=19539/

a) x : 12 = 10

    x        = 12 . 10

    x        = 120

b) 159 : n = 3

             n = 159 : 3

             n = 53

c) (x - 3) - 7 = 63

     x - 3 - 7  = 63

     x - 10     = 63

     x            = 63 + 10

     x            = 73

a) x = 120

b) n = 53

c) x - 3 = 70

x = 73

a) \(x+5=20-\left(12-7\right)\)

\(\Rightarrow x+5=20-5\)

\(\Rightarrow x+5=15\)

\(\Rightarrow x=15-5\)

\(\Rightarrow x=10\)

b) \(15-\left(3+2x\right)=2^2\)

\(\Rightarrow3+2x=15-4\)

\(\Rightarrow3+2x=11\)

\(\Rightarrow2x=11-3\)

\(\Rightarrow2x=8\)

\(\Rightarrow x=\dfrac{8}{2}\)

\(\Rightarrow x=4\)

c) \(-11-\left(19-x\right)=50\)

\(\Rightarrow19-x=-11-50\)

\(\Rightarrow19-x=-61\)

\(\Rightarrow x=61+19\)

\(\Rightarrow x=80\)

d) \(159-\left(25-x\right)=43\)

\(\Rightarrow25-x=159-43\)

\(\Rightarrow25-x=116\)

\(\Rightarrow x=25-116\)

\(\Rightarrow x=-91\)

e) \(\left(79-x\right)-43=-\left(17-52\right)\)

\(\Rightarrow\left(79-x\right)-43=52-17\)

\(\Rightarrow79-x-43=35\)

\(\Rightarrow36-x=35\)

\(\Rightarrow x=1\)

f) \(\left(7+x\right)-\left(21-13\right)=32\)

\(\Rightarrow7+x-8=32\)

\(\Rightarrow x-1=32\)

\(\Rightarrow x=32+1\)

\(\Rightarrow x=33\)

g) \(-x+20=-15+8+13\)

\(\Rightarrow-x+20=6\)

\(\Rightarrow x=20-6\)

\(\Rightarrow x=14\)

h) \(-\left(-x+13-142\right)+18=55\)

\(\Rightarrow x-13+142+18=55\)

\(\Rightarrow x+147=55\)

\(\Rightarrow x=55-147\)

\(\Rightarrow x=-92\)

a) đề bài => \(\frac{159-x}{141}+1+\frac{157-x}{143}+1+...+\frac{151-x}{149}+1=0\)

=>\(\frac{300-x}{141}+\frac{300-x}{143}+...+\frac{300-x}{149}=0\)

=>\(\left(300-x\right).\left(\frac{1}{141}+\frac{1}{143}+...+\frac{1}{149}\right)=0\)

vì \(\frac{1}{141}+\frac{1}{143}+...+\frac{1}{149}\ne0\)

=> \(300-x=0\)

=>\(x=300\)

chờ mình chút sẽ có câu b. k cho mình nha.

( 7 . 5 . 159 . 5 . 41 - 15 + 35 ) : 35

= ( 35 . 159 . 5 . 41 - 15 + 35 ) : 35

= ( 5565 . 5 . 41 - 15 + 35 ) : 35

= ( 27825 . 41 - 15 + 35 ) : 35

= ( 1140825 - 15 + 35 ) : 35

= ( 1140810 + 35) : 35

= 1140845 : 35

= sai đề