Maria needs to mix a 20% acid solution with a 60% acid solution to create 100 milliliters of a 56% solution. How many milliliters of each solution must Maria use?
Let x be the number of milliliters of the 20% acid solution.
So, 100 - x will be the number of milliliters of the 60% acid solution.
The amount of acid in the 20% acid solution is 0.2x.
The amount of acid in the 60% acid solution is 0.6(100 - x).
The total amount of acid in the final solution is 0.56(100).
So, the equation for the amount of acid is 0.2x + 0.6(100 - x) = 0.56(100).
Distribute 0.6 to get 0.2x + 60 - 0.6x = 56.
Combine like terms to get 60 - 0.4x = 56.
Subtract 60 from both sides to get -0.4x = -4.
Divide both sides by -0.4 to get x = 10.
Therefore, Maria must use 10 milliliters of the 20% acid solution and 100 - 10 = <<100-10=90>>90 milliliters of the 60% acid solution. Answer: \boxed{10, 90}.