Brett can plow out all the driveways on his street with his new four-wheel-drive truck in 33 hours. using a snow blade on a lawn tractor, his neighbor can plow out the same number of driveways in 77 hours. how long would it take them to do the work together?

In 1 hour brett can do 1/33 or (7/231) of the work
In 1 hour the neighbor can do 1/77 or (3/231) of the work

Together, in 1 hour, they can do 10/231 of the total work.

total work = 1
1/work per hour = 1/(10/231) = 231/10 hours =  23.1 hours to finish working together

4if you add the absolute values together