A scientist needs to make 2 liters of saline solution (salt water), in which the salt level must be at 15% concentration (meaning 15% of the water is salt). Unfortunately, the scientist only has two types of saline solution in his possession. He has saline solution with a 10% concentration level and saline solution with a 35% concentration level. How much of each type of saline solution should the scientist mix together to achieve 2 liters of saline solution at a concentration level of 15%?

Let xx represent the amount 10% saline solution and let yy represent the amount of 35% saline solution.