Question 1198027
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Joe works at the rate of  1/6 house per hour
Same works at the rate of 1/8 house per hour

Together (assuming they work without interfering with each other in any way), they work at the rate of  1/6 + 1/8  = 4/24 + 3/24 = 7/24 house per hour.

To paint one house (1 = 24/24), they take  (24/24)/(7/24) = 24/7 hours or about 3.42 hours (3hr 25min 43sec).

You can qualitatively sanity check this answer as follows:  notice each can paint the house individually in roughly 7 hours. For that rate you'd expect 3.5 hrs working together.  The obtained answer of 3.42hrs is close to this value, as one would (should) expect.