Bài 1 : tìm số tự nhiên x, biết: 8x + 15 =87 10+9x =109 7x – 8 =713 951 – 4x=83 98:x+25=39 802+x:3=919 235-x:8=123 1308+x:75=34 9x-7x=2018 23x-x=88 B

Question

Bài 1 : tìm số tự nhiên x, biết:
8x + 15 =87
10+9x =109
7x – 8 =713
951 – 4x=83
98:x+25=39
802+x:3=919
235-x:8=123
1308+x:75=34
9x-7x=2018
23x-x=88
Bài 2: Tìm số tự nhiên x, biết:
3.(x+25)=60
(18+x).9=270
2.(37-x)=42
(109-x).8=96
4.(x-29)=200
(x-27).7=84
94:(x+11)=2
(15+x):14=5
75:(39-x)=15
(918-x):5=25
129:(x-7)=43
(x-28):6=12

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Nem 4 years 2020-12-01T02:58:41+00:00 2 Answers 70 views 0

Answers ( )

    0
    2020-12-01T02:59:47+00:00

    Bài 1:

    a) 8x+15=87

    8x=87-15

    8x=72

    x=72:8

    x=9

    b) 10+9x=109

    9x=109-10

    9x=99

    x=99:9

    x=11

    c) 7x-8=713

    7x=713+8

    7x=721

    x=721:7

    x=103

    d) 951-4x=83

    4x=951-83

    4x=868

    x=217

    e) 98:x+25=39

    98:x=39-25

    98:x=14

    x=98:14

    x=7

    f) 802+x:3=919

    x:3=919-802

    x:3=117

    x=117.3

    x=351

    g) 235-x:8=123

    x:8=235-123

    x:8=112

    x=112.8

    x=896

    h) 1308+x:75=34

    x:75=1308-34

    x:75=1274

    x=1274.75

    x=95550

    i) 9x-7x=2018

    2x=2018

    x=2018:2

    x=1009

    k) 23x-x=88

    22x=88

    x=88:22

    x=4

    Bài 2:

    a) 3.(x+25)=60

    x+25=60:3

    x+25=20

    x=20-25

    x=-5

    b) (18+x).9=270

    18+x=270:9

    18+x=30

    x=30-18

    x=12

    c) 2.(37-x)=42

    37-x=42:2

    37-x=21

    x=37-21

    x=16

    d) (109-x).8=96

    109-x=96:8

    109-x=12

    x=109-12

    x=97

    e) 4.(x-29)=200

    x-29=200:4

    x-29=50

    x=50+29

    x=79

    f) (x-27).7=84

    x-27=84:7

    x-27=12

    x=12+27

    x=39

    g) 94:(x+11)=2

    x+11=94:2

    x+11=47

    x=47-11

    x=36

    h) (15+x):14=5

    15+x=5.14

    15+x=70

    x=70-15

    x=55

    0
    2020-12-01T03:00:09+00:00

    Đáp án:

    Bài 1.

    1.  8x +15 = 87

    ⇔ 8x = 87-15

    ⇔ 8x = 72

    ⇔ x = 72 : 8

    ⇔ x = 9

    2. 10 + 9x = 109

    ⇔ 9x = 109 – 10

    ⇔ 9x = 99

    ⇔ x = 99 : 9

    ⇔ x = 11

    3. 7x – 8 = 713

    ⇔ 7x = 713+8

    ⇔ 7x = 721

    ⇔ x = 721 : 7

    ⇔ x = 103

    4.  951 – 4x = 83

    ⇔ 4x = 951 – 83

    ⇔ 4x=868

    ⇔  x=217

    5. 98 : x + 25 = 39

    ⇔ 98 : x = 39-25

    ⇔ 98 : x = 14

    ⇔ x = 98 : 14

    ⇔ x=7

    6. 802 + x : 3 = 919

    ⇔ x : 3 = 919 – 802

    ⇔ x : 3 = 117

    ⇔ x = 117 × 3

    ⇔ x = 351

    7.   235 – x : 8 = 123

    ⇔ x : 8 = 235 – 123

    ⇔ x  : 8 = 112

    ⇔ x = 112×8

    ⇔ x = 896

    8.  1308 + x : 75 = 34

    ⇔ x : 75 = 1308 – 34

    ⇔ x : 75 = 1274

    ⇔ x = 1274× 75

    ⇔ x = 95550

    9. 9x – 7x = 2018

    ⇔ (9 – 7)x = 2018

    ⇔ 2x = 2018

    ⇔ x = 2018 : 2

    ⇔ x=1009

    10.  23x – x = 88

    ⇔ (23 – 1)x = 88

    ⇔ x =88 : 22

    ⇔ x = 4

    Bài 2

    1.  3.(x+25)=60

    ⇔ x + 25 = 60 : 3

    ⇔ x + 25 = 20

    ⇔ x = 20-25

    ⇔ x=-5

    2.    (18 + x  ).9 = 270

    ⇔18 + x = 270:9

    ⇔18 + x = 30

    ⇔x = 30 – 18

    ⇔ x = 12

    3.    2.(37-x) = 42

    ⇔ 37 – x = 42 : 2

    ⇔ 37 – x = 21

    ⇔ x = 37-21

    ⇔ x = 16

    4.   (109 – x).8 = 96

    ⇔ 109 – x = 96:8

    ⇔ 109 – x = 12

    ⇔ x = 109-12

    ⇔ x = 97

    5.  4.(x – 29) = 200

    ⇔ x – 29 = 200 : 4

    ⇔ x – 29 = 50

    ⇔ x = 50 + 29

    ⇔ x = 79

    6. (x-27).7 = 84

    ⇔ x – 27 =84 : 7

    ⇔ x – 27 = 12

    ⇔ x = 12 + 27

    ⇔ x = 39

    7. 94 : (x + 11) = 2

    ⇔ x + 11 = 94 : 2

    ⇔ x + 11 = 47

    ⇔ x = 47-11

    ⇔ x = 36

    8. (15 + x ) : 14 = 5

    ⇔ 15 + x = 5.14

    ⇔ 15 + x = 70

    ⇔ x = 70 – 15

    ⇔ x = 55

     9. 75 : (39 – x) = 15

    ⇔ 39 – x = 75 : 15

    ⇔ 39 – x = 5

    ⇔ x = 39 – 5

    ⇔ x = 34

    10.  (918 – x) : 5 = 25

    ⇔ 918 – x = 25.5

    ⇔ 918 – x = 125

    ⇔ x = 918 – 125

    ⇔ x = 793

    11.  129 : (x – 7) = 43

    ⇔ x – 7 = 129 : 43

    ⇔ x – 7 = 3

    ⇔ x = 10

    12.  (x – 28) : 6  = 12

    ⇔ x – 28 = 12 . 6

    ⇔ x – 28 = 72

    ⇔ x = 72 + 28

    ⇔ x = 100

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