Ineed to know what the variable of x is explain

Can someone me with this problem i don't understand i need

According to the data set, where should the upper quartile line of the box plot be placed?

Ebuka's monthly rent is $750. if ebuka pays the rent late, his landlord charges 4% interest per week that the payment is late. write a function that gives the total cost r(t), in dollars, of ebuka's rent if he pays it t weeks late.