Choosing numbers at random - expected value calculation From set $\{1,2,\ldots,49 \}$ we choose at random 6 numbers without replacing them. Let X denotes quantity of odd numbers chosen. Find $\mathbb{E}X$, how to find that? I have no idea whatsoever. 
EDIT:: still looking for the sufficient explanation. 

Let $X_1, X_2, X_3, X_4, X_5, X_6$ be $0$ or $1$ according to whether the $i$th choice is even or odd.  So $X=X_1+\cdots+X_6$.  You can now use linearity of expectation.
