The cost ,in dollars ,of renting a locker is a function of the time duration of the rental t in hours. the function c(t) outputs the cost c of a rental lasting t hours

how can the statement c(1.5)=9 be interpreted?

Well c is the cost to rent the locker for 1 hour, the 1.5 is the rental time, so multiplied together, you get the 9 which is the total cost to rent the locker for the number of hours you had it for.

for example: if you were to rent the locker for 1 hour (t = 1) the equation would look like c(1) = total cost.

*hopefully this is making sense*

another example: if you wanted to find out what the base rate is to rent the locker for 1 hour, you would just solve for c in the given equation
      
         c(1.5) = 9    c = 9/1.5   c = 6