The setup
Volume (mL) ÷ Rate (mL/hr) = Time (hr)
Then change the part of an hour into minutes by multiplying by 60.
500 ÷ 75 = 6.666… hr; 0.666… × 60 = 40 min → 6 hr 40 min
A common mistake
6.67 hr is not 6 hr 67 min. The decimal part is a fraction of an hour and must be multiplied by 60.
Enter hours and minutes in separate boxes. When the time does not come out to a whole minute, the question tells you to round to the nearest minute.