<h2>
Hello!</h2>
The answer is:
It will take 7.5 hours to paint the room together.
<h2>
Why?</h2>
Using the given information we need to write an equation considering both Colleen and Rebecca rates.
For Colleen we know that she can paint a room in 12 hours, so, her equation will be:
Being "t" the time used to paint.
For Rebecca, we know that she can paint a room in 20 hours, so, her equation will be:
Now, if we want to calculate the time needed to paint 1 room, we have:
Hence, we have that it will take 7.5 hours to paint the room together.
Have a nice day!