SOLUTION: I have solved similar linear equations previously, but this one stumps me. The answer is 4L per the book, but I cannot get to that answer. Here is the question: How many liters o

Algebra ->  Algebra  -> Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: I have solved similar linear equations previously, but this one stumps me. The answer is 4L per the book, but I cannot get to that answer. Here is the question: How many liters o      Log On

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Question 159456: I have solved similar linear equations previously, but this one stumps me. The answer is 4L per the book, but I cannot get to that answer. Here is the question:
How many liters of a 60% acid solution must be mixed with a 75% acid solution to get 20L of a 72% solution?
Answer by scott8148(5895) About Me  (Show Source):
You can put this solution on YOUR website!
let x="liters of 60%", so 20-x="liters of 75%"

(60%)(x)+(75%)(20-x)=(72%)(20) __ .6x+15-.75x=14.4 __ -.15x=-.6 __ x=4