Question

Anyone? I know I am way over thinking this

Answer 1

The original 30 workers get the job done in 20 days which means in one day one worker does 1/30th of 1/20th of the job per day or 1/600 per day the new workers will do 1/1200 per day since they are only half as good.

Answer 2

I would use
rate * time = 1 project
and put in # of people:
N * rate * time = 1

using N=30, time= 20 days
rate= 1/600 project / day
for the fast guys

and 1/1200 for the slow guys

Answer 3

Looks like phi and I both agree

Answer 4

care to try to set up an equation using those rates ?