Henry can lay a brick walkway by himself in 12 hours. Roberts does the same job in 10 hours. Working together, how long will it take them to lay the brick walkway?

Please I need the answer right away!

Henry = 12 hours        

Robert = 10 hours

that 2 people

so 12/ divided by how many people

and 10/ divided by how many people

so 12/2

and 10/2

= 5 and 6

then find the (median) middle of both numbers one or more  

which is 5 1/2

so they can finish working together in 5 1/2 hours