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Homework Help: [Linear Algebra] - Resolving a system

  1. Jul 26, 2011 #1
    1. The problem statement, all variables and given/known data

    Three truck drivers went into a roadside cafe. One truck driver purchased four sandwiches, a cup of coffee and ten doughnuts for $8.45. Another drivers purchased three sandwiches, a cup of coffee and seven doughnuts for $6.3. What did the third truck driver pay for a sandwich, a cup of coffee and a doughnut?

    2. Relevant equations

    3. The attempt at a solution

    The system's equations are:
    4s + 1c + 10d = 8.45
    3s + 1c + 7d = 6.3
    1s + 1c + 1d = a

    The system has infinite solutions, right? There are 4 variables for 3 equations. I can't determine a.
    Last edited: Jul 26, 2011
  2. jcsd
  3. Jul 26, 2011 #2


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    Homework Helper

    I don't think 'a' is intended to be a variable. I believe the objective is to solve for x,y, z in terms of 'a'. Thus, 3 equations and 3 unknowns.
  4. Jul 26, 2011 #3
    I wrote the problem wrongly on the first time, I just edited it.
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