let

p = L of pure acid

s = L of 10% solution

pure acid is to be added to a 10% solution to obtain 90 L of 44% solution

p + s = 90

p + 0.10s = 0.44*90

by solving the above system of equations we find

p = 34 L

s = 56 L

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we should use 34 liters of pure acid and 56 liters of 10% solution.