tìm x, biết : 100-7(x-5) = 58
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\(a,565-\left(6x+70\right)=435\)
\(6x+70=565-435\)
\(6x+70=130\)
\(6x=130-70\)
\(6x=60\)
\(x=10\)
\(b,100-7\left(x-5\right)=58\)
\(100-7x+35=58\)
\(100-7x=58-35\)
\(100-7x=23\)
\(7x=100-23\)
\(7x=77\)
\(x=11\)
a, 565-(6x+70)=435
6x+70=565-435
6x+70=130
6x=130-70
6x=60
x=60:6
x=6
b, 100-7(x-5)=58
7(x-5)=100-58
7(x-5)=42
x-5=42:7
x-5=6
x=6+5
x=11
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a. 348 : x = 12
x = 348 : 12
x = 29
b. 9x - 7 = 119
9x = 119 + 7
9x = 126
x = 126 : 9
x = 14
c. 100 - 7 . ( x - 5 ) = 58
7 . ( x - 5 ) = 100 - 58
7 . ( x - 5 ) = 42
x - 5 = 42 : 7
x - 5 = 6
x = 6 + 5
x = 11
d. x không thuộc số tự nhiên
a)348:x=12
x=348:12
x=29
b)9x-7=119
9x=119+7
9x=126
x=126:9
x=14
c)100-7.(x-5)=58
7.(x-5)=100-58
7.(x-5)=42
x-5=42:7
x-5=6
x=6+5
x=11
d)2x-2.23=64
2x-2.8=64
2x-16=64
2x=64+16
2x=80
đề sai
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a ) 100-7(x-5)=58
=> 7(x-5)=42
=.> x-5 = 6
=> x=11
180-5(x+1)=30
=> 5(x+1)=150
=> x+1=30\
=> x=29
6x-5=613
=> 6x=618
=> x=103
a) \(100-7\left(x-5\right)=58\)
\(\Leftrightarrow7\left(x-5\right)=42\)
\(\Leftrightarrow x-5=6\)
\(\Leftrightarrow x=11\)
b) \(180-5\left(x+1\right)=30\)
\(\Leftrightarrow5\left(x+1\right)=150\)
\(\Leftrightarrow x+1=30\)
\(\Leftrightarrow x=29\)
c) \(6x-5=613\)
\(\Leftrightarrow6x=618\)
\(\Leftrightarrow x=103\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1) (x - 35) - 120 = 0
x - 35 = 120
x = 120 + 35
x = 155
2) 310 - (118 - x) = 217
118 - x = 310 - 217
118 - x = 93
x = 118 - 93
x = 25
3) 156 - (x + 61) = 82
x + 61 = 156 - 82
x + 61 = 74
x = 74 - 61
x = 13
4) 814 - (x - 305) = 712
x - 305 = 814 - 712
x - 305 = 102
x = 102 + 305 = 407
5) 100 - 7 - (x - 5) = 58
x - 5 = 93 - 58
x - 5 = 35
x = 35 + 5 = 40
6) 12(x - 1) : 3 = 43 + 23
4(x - 1) = 72
x - 1 = 18
x = 18 + 1 = 19
7) 24 + 5x = 75 : 73
24 + 5x = 49
5x = 25
x = 25 : 5 = 5
8) 5(x - 1) : 3 = 43 + 23
\(\dfrac{5}{3}\left(x-1\right)=72\)
x - 1 = \(\dfrac{216}{5}\)
x = 221/5
9) 5(x - 4)2 - 7 = 13
5(x - 4)2 = 20
(x - 4)2 = 4
\(\Rightarrow\left[{}\begin{matrix}x-4=2\\x-4=-2\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=6\\x=2\end{matrix}\right.\)
10) (x + 1) + (x + 2) + ... + (x + 30) = 795
=> (x + x + x + ... + x) + (1 + 2 + 3 +...+ 30) = 795 (1)
Đặt A = 1 + 2 + 3 +...+ 30
Số số hạng trong A là: (30 - 1) : 1 + 1 = 30 (số)
Tổng A bằng : (30 + 1).30 : 2 =465
Thay A = 465 vào (1) , ta được:
30x + 465 = 795
=> 30x =330
=> x =11
1: =>x-35=120
=>x=120+35=155
2: =>118-x=310-217=93
=>x=118-93=25
3: =>x+61=156-82=74
=>x=74-61=13
4: =>x-305=814-712=102
=>x=102+305=407
5: =>93-(x-5)=58
=>x-5=35
=>x=40
6: =>4(x-1)=64+8=72
=>x-1=18
=>x=19
7: =>5x+24=49
=>5x=25
=>x=5
8: =>5(x-1):3=4^3+2^3=64+8=72
=>5(x-1)=216
=>x-1=216/5
=>x=221/5
![](https://rs.olm.vn/images/avt/0.png?1311)
a: Ta có: \(100-7\left(x-5\right)=58\)
\(\Leftrightarrow7\left(x-5\right)=42\)
\(\Leftrightarrow x-5=6\)
hay x=11
b: Ta có: \(12\left(x-1\right):3=4^3+2^3\)
\(\Leftrightarrow12\left(x-1\right)=216\)
\(\Leftrightarrow x-1=18\)
hay x=19
100 - 7 . ( x - 5 ) = 58
93 . x - 5 = 58
x - 5 =93 : 58
x - 5 = 1.6
x = 1.6 +5
x = 6.6
100-7.(x-5)=58
7.(x-5)=100-58
7.(x-5)=42
x-5=42:7
x-5=7
x=7+5
x=12
vậy x=12