Answer: 5 hours and 20 minutes.
Explanation:
Let be "x" the time in hours that will take to paint
of the room.
You know that 8 hours is the time it takes to paint the room.
With this information you can set up the following proportion:

Finally, you must solve for the variable "x" in order to find its value.
You get that this is:

Since:

You can determine that:

Then, the answer is: 5 hours and 20 minutes.