What is probability of language knowledge in company? In a company are 100 workers.


50 of them (100) speak ENG 
30 of them (100) speak GER 
15 of them (100) speak ENG and GER


What is the probability of randomly selected worker speaks GER on condition he does NOT speaks ENG?

I have two suggestions:


a) 3/10  
b) lower than 3/10
As described in the problem, a worker speaking German and a worker speaking English are independent events. As such, the fact that a worker speaks English doesn't actually give you any information as to whether or not a worker speaks German. Thus, the odds that a worker speaks German given that he speaks English is the same as the odds that a worker speaks German: $\frac{3}{10}$
ENG          Non-ENG
☺☺☺☺☺☺☺☺☺☺ | ☺☺☺☺☺☺☺☺☺☺
☺☺☺☺☺☺☺☺☺☺ | ☺☺☺☺☺☺☺☺☺☺
☺☺☺☺☺☺☺☺☺☺ | ☺☺☺☺☺☺☺☺☺☺
☻☻☻☻☻☺☺☺☺☺ | ☻☻☻☻☻☺☺☺☺☺
☻☻☻☻☻☻☻☻☻☻ | ☻☻☻☻☻☻☻☻☻☻


☻ =  GER

The odds of randomly selecting a GER speaker out of the total are $3/10$ (30 GER out of 100 workers) and half of the workers also speak ENG.

Therefore, the odds of a randomly selected worker speaking GER and not ENG are $1/2$(Fraction of workers that don't speak ENG) times 3/10(fraction of workers that speak GER).

$.15$ or $3/20$