given the function of the income is ;
[tex]f(x)=-3x^2+55x[/tex][tex]E(x)=7x+144[/tex]to get maximum profit f(x) = E(x)
[tex]\begin{gathered} -3x^2+55x=7x+144 \\ -3x^2+55x-7x-144=0^{} \\ -3x^2+48x-144=0 \end{gathered}[/tex]Divide all terms by -3:
[tex]x^2-16x+48=0[/tex]Factor the last equation :
[tex]\begin{gathered} (x-4)(x-12)=0 \\ x=4 \\ or \\ x=12 \end{gathered}[/tex]As 12 > 4
The price of the ticket = $12