Hi!
Let's find how many dishes the chefs can prepare in 1 hour.
10 x 6 = 60
They work 60 hours in 10 days.
1,500/60 = 25
They cook 25 dishes in one hour.
If 420 chefs are working 8 hours a day, for 18 days they can prepare how many dishes?
18 x 8 = 144
144 hours in 18 days.
144 x 25 = 3600
You can prepare 3600 dishes in 18 days.
Hope this helps! :)