x + 80 = 15 + 159
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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
![](https://rs.olm.vn/images/avt/0.png?1311)
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
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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
![](https://rs.olm.vn/images/avt/0.png?1311)
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) \(-\left(-x+13-142\right)+18=55\)
\(\Rightarrow x-13+142+18=55\)
\(\Rightarrow x+147=55\)
\(\Rightarrow x=55-147\)
\(\Rightarrow x=-92\)
![](https://rs.olm.vn/images/avt/0.png?1311)
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.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
( 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
x+80=15+159
x+80=174
x=174-80
x=94
x + 80 = 15 + 159
x + 80 = 174
x = 174 - 80
x = 94