Two cars got an oil change at the same auto shop. The shop charges customers for each quart of oil plus a flat fee for labor. The oil change for one car required 5 quarts of oil and cost $21.90. The oil change for the other car required 7 quarts of oil and cost $25.40. How much is the labor fee and how much is each quart of oil?

Step-by-step explanation:

Let x = the fee and let y = the cost per quart of oil

x + 5y = 22.45

x + 7y = 25.45     Multiply this equation by (-1) and add it to the 1st equation

-x -7y = -25.45

x + 5y = 22.45

     -2y = -3

        y = $1.50 /quart

x + 5(1.50) = 22.45

     x + 7.50 = 22.45

                 x = $14.95   is the basic fee

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step-by-step explanation:

-2x + 7 = 7

subtract 7 from both sides.

-2x = 0

divide both sides by -2.

x = 0