Shamus can paint the barn in 6 hours, and ishmael can paint the barn in 7 hours. how long will it take them to paint the barn together?

Given that Shamus can paint the barn in 6 hours, the portion of barn he can complete in 1 hour will be 1/6

If Ishmael can paint the ban in 7 hours, the portion he can paint is 1/7

when working together the portion they can complete will be:

1/7+1/6

=13/42

time taken for them to complete the barn will be:

42/13

=3 3/13 hours

the answer is 3 3/13 hours