writing and solving equations

Discussion in 'Calculator Requests' started by TinaJena, Dec 9, 2016.

  1. TinaJena

    TinaJena New Member

    My daughter is having issues with a math problem for her homework. she tells me that I am doing it wrong but I am getting the correct answer... Can you please look at it and see if i am correct?
    The problem is:
    A painter charges $15.35 per hour, plus an additional amount for supplies. If he made $141.73 on a job where he worked 4 hours, how much did the supplies cost?

    I have the equation as: $15.35 * 4 = $141.73 - x ... I got the answer of $80.33 for supplies

    She is telling me that the teacher is wanting her to do the PEMDAS backwards but that is not working out for her and I am not understanding that at all. Any suggestions would help out


  2. math_celebrity

    math_celebrity Administrator Staff Member

    Your answer is correct.

    Here is how I set up the profit equation where h is the hours worked and x is the supply cost:
    P(h) = 15.35h + x

    We know P(4) = 141.73
    P(4) = 15.35(4) + x
    141.73 = 15.35(4) + x

    141.73 = 61.4 + x

    Subtract 61.4 from each side:
    x = 80.33

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