algebra 1

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plz explain how to do this in detail:

using only 39 cent and 24 cent stamps, charlie put $7.14 postage on a package he mailed to his sister. if he used twice as many 39 cent stamps as 42 cent stampsp, how many 24 cent stamps did he use??

  • algebra 1 -

    first represent the unknowns using variables:
    let x = number of 24-cent stamps used
    let 2x = number of 39-cent stamps used (according to the second statement)
    since the total is 7.14 dollars,
    0.24x + 0.39(2x) = 7.14
    now we solve for x:
    0.24x + 0.78x = 7.14
    1.02x = 7.14
    x = 7 (number of 24-cent stamps used)

    hope this helps~ :)

  • algebra 1 -

    Triple a number plus 7 results in 16. What is the number?

  • for the 2nd question -

    let x = number
    according to the first statement, we multiply the number by three, then we add 7 to get 16,, writing in equation:
    3x + 7 = 16
    now solve for x,, first we transpose the 7 on the other side of equation,, to do this we change its sign from positive to negative:
    3x = 16 - 7
    3x = 9
    to get x alone, we divide both side of equation by 3:
    (3x)/3 = 9/3
    x = 3

    hope this helps~ :)

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