Inverse and Direct Variation Word Problems - Examples

Jess is making some lemonade for a school event. She wants to use up all of her $0.2$ liters of lemon concentrate. What is the relationship between the percentage of concentrate in lemonade and the total volume of lemonade (water plus lemon concentrate) Jess makes? If Jess wants the percentage to be about $15\%$, how much water should she use?