It takes 12 hours to clean the windows of a certain office building. During the
first day of cleaning, the workers were able to clean for 9 hours. If the variable
t stands for the amount of time the workers have left to clean the windows,
which of the following choices is the most reasonable value for ?
O A. 20 hours
O B. 3 hours
O C. 1 hour
O D. 30 hours