MATH EQUATIONS HELP!!?

Hi! I'm having trouble with these three math equations. I've done them all a few times, but I can't seem to get them right. Will somebody please help me? I'll choose best answer!

1. 6(14 - 3x) +20x=90

2. 2/3x +15 = 1/2x +4

3. 2.9n + 1.7 = 3.5 + 2.3n

Thanks! :D

16 Answers

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  • gab BB
    Lv 6
    1 decade ago
    Best Answer

    1.

    6(14 - 3x) +20x=90

    84-18x+20x = 90

    84+2x = 90

    (84+2x)-84 = 90-84

    84+2x-84 = 6

    84-84+2x = 6

    2x = 6

    (2x)/2 = 6/2

    x = 3

    2.

    2/3x +15 = 1/2x +4

    I assume that you mean

    (2/3)x +15 = (1/2)x +4

    [(2/3)x +15]-(1/2)x-15 = [(1/2)x+4]-(1/2)x-15

    (2/3)x-(1/2)x = -11

    (2/3)x*6-(1/2)x*6 = -11*6

    4x-3x = -66

    x = -66

    3.

    2.9n + 1.7 = 3.5 + 2.3n

    (2.9n+1.7)-2.3n-1.7 = (3.5+2.3n)-2.3n-1.7

    2.9n-2.3n+1.7-1.7 = 2.3n-2.3n+3.5-1.7

    0.6n = 1.8

    (0.6n)/0.6 = 1.8/0.6

    n = 1.8/0.6

    n = (1.8*10)/(0.6*10)

    n = 18/6

    n = 3

    HOPE THIS HELPS.

  • 1 decade ago

    1. 6(14 - 3x) +20x=90

    6*14 - 6*3x + 20x = 90, distributive property

    84 - 18x + 20x = 90

    84 + 2x = 90, combine like terms

    2x = 6, additive inverse on both sides

    x = 3, divide by 2

    2. 2/3x +15 = 1/2x +4

    2/3x - 1/2x + 15 = 1/2x - 1/2x + 4

    2/3x - 1/2x + 15 = 4

    2/3x - 1/2x + 15 - 15 = 4 - 15

    2/3x - 1/2x = -11

    4/6x - 3/6x = -11, common denominator

    1/6x = -11

    x = -11 * 6 = -66

    3. 2.9n + 1.7 = 3.5 + 2.3n

    29n + 17 = 35 + 23n, multiplied entire equation by 10

    29n - 23n + 17 = 35 + 23n - 23n

    29n - 23n + 17 = 35

    29n - 23n + 17 - 17 = 35 - 17

    29n - 23n = 35 - 17

    6n = 18

    n = 3

  • 1 decade ago

    1) 84 - 18x+20x = 90

    -18x+20x = 90-84

    2x = 6

    x= 6/2

    x=3

    2) 2/3x-1/2x= 4-15

    1/6x = -11

    x= -66

    3) 2.9n -2.3n = 3.5 - 1.7

    0.6n = 1.8

    n = 3

  • 1 decade ago

    1. Distribute the 6, so you get 84 - 18x + 20x = 90

    then combine like terms -18x + 20x = 90 - 84

    so 2x = 6

    and x = 3

    2. Multiply everything by 6, so you get 4x + 90 = 3x + 24

    then combine like terms so you have 4x - 3x = 24 - 90

    so x = -66

    3. Combine like terms: 2.9n - 2.3n = 3.5 - 1.7

    .6n = 1.8

    n = 3

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  • 1 decade ago

    1]

    6*14-6*3x+20x=84-18x+20x=90

    this implies 2x=90-84=6

    this in turn implies 2x=6

    hence x=6\2=3

    therefore x=3

    2]

    2\3x+15=1\2x+4

    shifting places n getting all "x"terms on one side of the equation we get

    2\3x-1\2x=4-15

    take lcm of 3x and 2x

    it is 6x

    so 4-3\6x=-11

    1\6x=11

    6x=1\11

    x=1\11*6

    x=1\66

    3]

    2.9n-2.3n=3.5-1.7{this we got after shifting places on either side of equal to sign}

    after that

    0.2n=2.5

    n=2.5\0.2

    hence n=12.5

    that's it dude,did you get me,the answers are correct

  • 1 decade ago

    6(14 - 3x) + 20x = 90

    84 -18x +20x = 90 # subtract 84

    2x = 6

    x = 3

    ---

    2/3x +15 = 1/2x +4 # multiply with 6

    4x + 90 = 3x + 24 # subtract 3x, subtract 90

    x = -66

    ---

    2.9n + 1.7 = 3.5 + 2.3n # subtract 2.3n, subtract 1.7

    0.6n = 1.8

    n = 3

  • 1 decade ago

    1. 84-18x+20x=90

    84+2x=90

    2x=6

    x=3

    2. 4x+90=3x+24

    x+90=24

    x= -66

    3. 2.6n=1.8

    n=0.69 (sorry i dont think this one is right though)

  • 1 decade ago

    84-18x+20x=90

    2x+84-84=90-84

    2x=6 x=3

    2/3x+15=1/2x+4

    3x+90=3x+24

    x=-66

    2.9n+1.7= 3.5+2.3n

    .6n=1.8

    n=3

  • Anonymous
    1 decade ago

    1.

    6(14-3x)+20x=90

    84-18x+20x=90

    -18x+20x=6

    2x=6

    x= 3

    2.

    2/3x+15=1/2x+4

    2/3x-1/2x=4-15

    1/6x=-11

    x= -66

    3.

    2.9n + 1.7 = 3.5 + 2.3n

    2.9n-2.3n=3.5-1.7

    .6n=1.8

    n = 3

  • 1 decade ago

    1. x=3

    2. x=-66

    3. n=3

    Source(s): this is easy 7th grade algebra.... and my current math teacher is the bomb!
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