Ten people can paint 60 houses in 120 days, so five people can paint 30 houses in:

Answer 1

everything is halved so 120/2= 60 days

Answer 2

The sixty houses take (10 men)(120 days) = 1200 man-days to complete. Then one house would take (1200 man-days) / (60 houses) = 20 man-days / house.

How many man-days are required for thirty houses?

If those man-days are divided amongst five people, how many days must each person spend?