an automobile radiator contains 20 L of antifreeze and water. this mixture is 20% antifreeze. how much of this mixture should be drained and replaced with pure antifreeze so that the mixture will be 50% antifreeze.
Try this solution (this suggested way is not short, but pure): 1. to make up the scheme of changes; 2. to make up the system of the equations according to the scheme.
Note, that antifreeze is marked by black in the picture.
