40(105/100)=42
.........................
Answer: 12 hours
Step-by-step explanation:
Given : Working together, it takes Sam, Jenna, and Francisco two hours to paint one room.
When Sam works alone, he can paint one room in 6 hours. When Jenna works alone, she can paint one room in 4 hours.
Let 't' be the time taken by Francisco to paint one room on his own.
Then , we have
Rate of work of Sam +Rate of work of Jenna + Rate of work of Francisco =Rate of work they all do together

i.e. 
i.e. 
i.e. 
i.e. 
i.e. 
i.e. 
i.e. t= 12
Hence, Francisco would take 12 hours to paint one room on his own.
1347.25 just easily divide to get your answer. Nothing else :)
Let's start by understanding that the graph is a linear line. We have a common difference if 4.5 for every 10x we have more.
We can start by finding the gradient, using rise over run. Let's take (10, 4.5) and (20, 9)
Our rise is 9 - 4.5 = 4.5 and our run is 10. Then, our gradient becomes 4.5/10 = 0.45
Now, we can substitute points using the point-slope form.
y - 4.5 = 0.45(x - 10)
y - 4.5 = 0.45x - 4.5
Hence, our line becomes y = 0.45x and you can verify by substituting in points from the table.
The answer is that (It’s 6.6)