The number of non-bouncers is $(.12)(47000)=5640$, which also means that the number who do bounce is $47000-5640 = 41360$. Let $A$ represent the average number of pages seen by a non-bouncer (what you want to solve for). Then you know that the total number of pages seen by the 47000 users is $(A)(5640)+(1)(41360) = 5640A +41360$. Therefore the average number of pages seen by all users is $$ \frac{5640A + 41360}{47000} $$ but you also know that this number is $1.23$. So, solve for $A$ in $$ \frac{5640A + 41360}{47000} = 1.23 $$