18x-18=0 

18x=0+18

18x=18

x=18:18

x=1

17(x-15)=0

(x-15)=0:17

(x-15)=0

x=15+0

x=15

(x-42) - 17 = 127

=> x - 42 = 127 + 17 = 144

=> x = 144 + 42 = 186

23(x+1) = 69

=> x + 1 = 69 : 23 = 3

x = 3 - 1 = 2

2x + 5 = 120 : 2 = 60

=> 2x = 60 - 5 = 55

x = 55 : 2 = 27,5

5x - 2 = 613

=> 5x = 613 + 2 = 615

x = 615 : 5 = 123

a)(x-42)-17=127

(x-42)=127+17

(x-42)=144

x=144+42

x=186

b)23(x+1)=69

(x+1)=69:23

(x+1)=3

x=3-1

x=2

c)2.x+5=120:2

2.x+5=60

2.x=60-5

2.x=55

x=55:2

x=27,5

d)5.x-2=613

5.x=613+2

5.x=615

x=615:5

x=123

(x-42)-17=127(tim x)xx

23(x+1)=69(timx)xx

2x+5=120:2(Timx)xx

5x-2=613(timx)xx

(15 + x) - 24 = 246

=> 15 + x = 246 + 24 = 270

x = 270 - 15 = 255

(298 - x) - 42 = 252

=> (298 - x) = 252 + 42 = 294

=> x = 298 - 2984 = 4

2x + 13 = 35

=> 2x = 35 - 13

2x = 22

x = 22 : 2

x  = 11

\(125\times x-x\times47=25350\\x\times(125-47)=25350\\x\times78=25350\\x=25350:78\\x=325\)

\(x\) + 78 x \(x\)+ 25 x \(x\)- \(x\)x 4 = 78,6 + 121,4

\(x\)x 1 + 78 x \(x\)+ 25 x \(x\)- \(x\)x 4 = 200

\(x\)x ( 1 + 78 + 25 - 4 ) = 200

\(x\)x 100 = 200

\(x\)= 200 : 100

\(x\)= 2

X + 78 * X + 25 * X - X * 4 = 78,6 + 121,4

X * ( 1 + 78 + 25 - 4 ) = 200

                     X * 100 = 200

                             X = 200 : 100

                            X = 2

                        Vậy X = 2 

Đáp án cần chọn là: B

x∈{−1;0;1;2;3;4;5}

5 6 + − 7 8 ≤ x 24 ≤ − 5 12 + 5 8 − 1 24 ≤ x 24 ≤ 5 24 − 1 ≤ x ≤ 5

- 7 8 + 5 6 < x 24 ≤ 5 8 + - 5 12

⇔ - 21 24 + 20 24 ≤ x 24 ≤ 15 24 + - 10 24 ⇔ - 1 24 ≤ x 24 ≤ 5 24

-1 ≤ x ≤ 5 mà x ∈ Z. Do đó: x ∈ { -1 ; 0 ; 1 ; 2 ; 3 ; 4 ; 5 }

-1 ≤ x ≤ 5 mà x ∈ Z. Do đó: x ∈ { -1 ; 0 ; 1 ; 2 ; 3 ; 4 ; 5 }