SOLUTION: Use given information to write a system of equations; then, solve the system. Be sure to clearly identify all unknowns in the equation. An auto mechanic student needs 25 gallons

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Question 366635: Use given information to write a system of equations; then, solve the system. Be sure to clearly identify all unknowns in the equation.
An auto mechanic student needs 25 gallons of a 21% antifreeze solution. She has available a 40% solution and a 15% solution. How much of each solution should she use to end up with 21% solution?

Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
25*.21=5.25
x*.40=.40x
(25-x)*.15=3.75-.15x
.
.40x+3.75-.15x=5.25
.25x=1.5
x=6 gal. of 40%
25-x=19 gal. of 15%
.
Ed