Question 655932
Ryan can paint a fence in 10 hours, so he can paint {{{1/10}}} of the fence in one hour.
Assanji can paint a fence in 8 hours, so he can paint {{{1/8}}} of the fence in one hour.

Together they can paint {{{1/10 + 1/8 = 4/40 + 5/40 = 9/40}}} fence in an hour.

So it will take them {{{1/(9/40) = 40/9 = 4&4/9}}} hours, or 4 hours, 26 minutes, 40 seconds to paint the fence.