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![enter image description here](https://i.stack.imgur.com/Yu7rX.jpg)

> 
> A survey conducted in the Documentation and Information Centre (CDI)
>  of a high school gives the following results: 60% of students
>  frequenting the CDI are girls and among them, 40% are in the second,
>  30% in the first and the remaining terminal. Among boys frequenting
>  the CDI, 50% are in the second, 20% in the first one and the rest in
>  the terminal.
> 
> 
> Were randomly questioned a high frequenting the CDI and we consider
>  the following events:
> 
> 
> F: "the pupil is a girl asks," G: "asks the pupil is a boy" S: "the
>  pupil is questioned in second" P: "is the first high interrogates" T:
>  "asks the pupil is terminal."
> 
> 
> Question 5- The pupil asks not to be from the second class . so what
>  is the probability $P\_{4}$ whether a boy
> 
> 
> 

beware if you don't understand my translation from the source you should wait until someone will translate it i tag translation-request

* I want to understand how they did to get

$$P\_{4}=0.3571$$

my attempts

since the student is not in second class so it is first or terminal class ....

Let E be the set of first or terminal class

$P(E)=P(F\cap P )P(F\cap T )+P(G\cap P )P(G\cap T )$ 

the probability that it is a boy not in the second class

$$P\_{E}(G) = \dfrac {P(E \cap G)}{P(E)}$$