Hi Vincen,
When dealing with these types of 'work' questions, it can be helpful to think in terms of the total amount of work that needs to be done to complete the given task. We're told that it takes 20 workmen 5 days to complete the task. That's...
(20 men)(5 days each) = 100 work-days of effort to create 35 widgets.
Thus, there are a number of different ways to complete that work:
1 worker can work for 100 days
2 workers can work for 50 days each
4 workers can work for 25 days each
Etc.
The question asks us to create 105 widgets, which is 3 times the 35 in the above calculation. Those 105 widgets would take 3(100) = 300 work-days of effort. If we have to complete the job in 5 days, then we can set up the following equation:
(X men)(5 days each) = 300 work-days
X = 60 men
Final Answer: E
GMAT assassins aren't born, they're made,
Rich