The goal of the amusement park is to appeal to people between the ages of 13 and 25. So far, the people who have bought tickets are 10

I am not sure what this question means   

$${\frac{\left({\mathtt{10}}{\mathtt{\,\small\textbf+\,}}{\mathtt{10}}{\mathtt{\,\small\textbf+\,}}{\mathtt{15}}{\mathtt{\,\small\textbf+\,}}{\mathtt{29}}{\mathtt{\,\small\textbf+\,}}{\mathtt{32}}\right)}{{\mathtt{5}}}} = {\frac{{\mathtt{96}}}{{\mathtt{5}}}} = {\mathtt{19.2}}$$   

At the moment the average age is 19.2 years

Maybe it means that the average has to be between 13 and 25     

$$\\13<\frac{96+X}{6}<25\\\\
78<96+X<150\\\\
0

But really the person should be between  13 AND 25

I think that this is a dumb question