If 8 men now 4 identical greens in 20 minutes, how many are needed to now a similar sized bowling greens in 1 hour?
so
1 man mows 4 greens in 160 min
1 man moves one green in 40 min
You did not say how many greens to mow in an hour so I can not continue, but you should be able to figure it out now that you have the data for one man