Jonah wants to buy two copies of a book. which algebraic expression could jonah use to find the value of the items

Damon makes 20 cups of lemonade by mixing lemon juice and water. the ratio of lemon juice to water is shown in the tape diagram. lemon juice\text{lemon juice} lemon juice water\text{water} water how much lemon juice did damon use in the lemonade? cups

Pls the last one and it has to be like number 6

What is the value for this expression? 2e-5