Maria needs to mix a $10 \%$ saline solution with a $60 \%$ saline solution to create 200 milliliters of a $30 \%$ solution. How many milliliters of each solution must Maria use? Answer: Maria must mix milliliters of $10 \%$ solution and milliliters of $60 \%$ solution.

Step 1 ：Let's denote the volume of the $10 \%$ solution as $x$ and the volume of the $60 \%$ solution as $y$.

Step 2 ：The total volume of the solution is 200 milliliters, so we have the equation \(x + y = 200\).

Step 3 ：The total amount of salt in the solution is $30 \%$ of the total volume, so we have the equation \(0.10x + 0.60y = 0.30 * 200\).

Step 4 ：We can solve these two equations simultaneously to find the values of $x$ and $y$.

Step 5 ：By solving the equations, we find that $x = 120$ and $y = 80$.

Step 6 ：Final Answer: Maria must mix \(\boxed{120}\) milliliters of $10 \%$ solution and \(\boxed{80}\) milliliters of $60 \%$ solution.