Question 666040
dan and betty can paint 2400sq ft in 4 hours. So that is 2400/4 = 600 sq ft per hour.
Betty can paint twice as much as dan, so {d + 2d = 600}}}
{{{d=600/3 = 200}}}
Dan can do 200 sq ft/hour. Bety can do twice that, 400sq ft/hour

Now you are told they get sue to help.
The three of them paint 3600 sq ft in 3 hours.
You know dan and Betty do 600 sq ft/hour. So the two of them will do 1800 sq ft in 3 hours. That mean sue does {{{3600 - 1800 = 1800}}} sq ft in 3 hours.
So sue does 600 sq ft /hour

Use that rate to see how much sue can paint in 4 hours 27 minutes (remember that 27 minutes is 27/60 of an hour