Question

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Answer 1

x = number of liters of the 20% acid solution
y = number of liters of the 70% acid solution


we want 50 liters total, so x+y = 50

solve for y: y = 50 - x

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There are 0.20x liters of pure acid plus another 0.70y liters of pure acid. We want "50 liters of a 40% solution." so 50*0.40 = 20. We want a total of 20 liters of pure acid

0.20x + 0.70y = 20

Answer 2

plug in y = 50 - x


0.20x + 0.70y = 20

0.20x + 0.70(50 - x) = 20


You now have to solve for x

Answer 3

once you find x, you need to find y using y = 50 - x