Question 665623
Without a lot of explanation, I'll give you the answer to this type of problem.
The combined effort two people that take x hrs and y hrs individually, will do the job in h hrs given by
(1) h = 1/(1/x + 1/y)
Applying this to your problem we get
(2) h = 1/(1/4 + 1/6) or
(3) h = 1/(6/24 + 4/24) or
(4) h = 1/(10/24) or
(5) h = 24/10 or 
(6) h = 2.4 hrs
Answer: It will take 2hr and 24min for them to paint the house together.