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.

The number of 8th graders who responded to a poll of 6th grade and 8 th graders was one fourtg of the number of 6th graders whi responded if a total of 100 students responddd to the poll how many of the students responded were 6 th graders