How many liters of a 20% solution of a chemical should be mixed with 15 liters of 50% solution to obtain a 30% mixture

20x + 50y = 30(x + y)y = 15---put the system of linear equations into standard form:---20x + 50y = 30x + 30yy = 15---10x - 20y = 0y = 15---x = 30 liters of 20%y = 15 liters of 50%---resulting solution: 45 liters of 30%