The workdone by the three(3) is equal to the painting of 1 room in 2 hours.
Time taken by
Carl alone = 5 hours
Cameron alone = 6 hours
Let time taken by Carlos alone = x hours
In One(1) hour, the size of the that will be covered by each of them is:

a) Hence, the equation that can be used to determine how long it would take Carlos to paint the room alone is:

b) We will solve for the value of x in the equation above

Hence, it will take Carlos 7.5 hours to paint the room alone