How do i solve? a chemist has 0.4 liters of an acid solution whose acid concentration is 80%. how many liters of pure water should be added to lower the concentration to 40%?

With #! i’ve tried to figure it out but i can’t.

The appalachian trail is a hiking trail that passes through the appalachian mountains. three members of a teen hiking group hiked a section of the trail. the hikers stopped at a rest area and equally shared 3 4 gallon of water. how much water did each person get?

What is the name used to describe a graph where for some value of x, there exists 2 or more different values of y?