Question: Solve the indicated or given systems of equations by an appropriate algebraic method.
A 6.0% solution and a solution of a drug are added to 200 mL of a 20.0% solution to make 1200 mL of a 12.0 % solution for a proper dosage.
The equations relating the number of milliliters of the added solutions are
x + y + 200 = 1200
Find x and y (to three significant digits).