David can paint the living room in 4 hours and Anna can paint it in 6 hours. How long will it take the two of them to paint the living room if they work together?

It will take them two hours to paint the living room.

12/5 = 2.4

Step-by-step explanation:

In 4 hours, David can paint 1 room

In (4/4) = 1 hour, David can paint 1/4 of the room

Similarly,

In 6 hours, Anna can paint 1 room

In 1 hour, Anna can paint 1/6 of the room

Therefore,

In one hour, they can paint (1/4 + 1/6) of the room if they work together

= 5/12

So,

They can paint 1 room in 12/5 hours

= 2.4 hours