A survey show that 63% of the people in a city read newspaper A whereas 76% read newspaper B. If x% of the people read both the newspapers, then a possible value of x can be

Suppose that there are 100 people are there in the city

Given $n\left(A\right)=63,n\left(B\right)=76,n(A\cap B)=x$

The addition theorem on cardinal number of sets 

           $n(A\cup B)=n\left(A\right)+n\left(B\right)-n(A\cap B)$

Substitute the apropriate values 

we get 

$\begin{array}{rcl}n(A\cup B)& =& n\left(A\right)+n\left(B\right)-n(A\cap B)\\ & =& 63+76-x\\ & =& 139-x\end{array}$

$A\subseteq A\cup B,B\subseteq A\cup B\Rightarrow n\left(A\right)\le n(A\cup B),n\left(B\right)\le n(A\cup B)$

Therefore, 

    $\begin{array}{rcl}76& \le & 139-x\le 100\\ -63& \le & -x\le -39\\ & & \boxed{39\le x\le 63}\end{array}$