The table in Part A represents y as a function of x. This means that the value of Y is dependent on the value of X. The table can be represented by an equation that describes the relation of X and Y:
or 
By substituting any value of X, you get a specific value of Y based from the given relationship, thus Y is a function of X.
For Part B, the value of f(150) is $470 and it represents the total cost for borrowing a rowboat for 150 hours. By substituting the value of x = 150 into the function, you get the total cost:
By substituting any value of X, you get a specific value of Y based from the given relationship, thus Y is a function of X.
For Part B, the value of f(150) is $470 and it represents the total cost for borrowing a rowboat for 150 hours. By substituting the value of x = 150 into the function, you get the total cost: