let the ticket price be plotted on the x-axis and the attendance on the y-axis. we have the points (12,26000) and (11,31000). we can use this to get the equation of the line that relates the ticket price, P, and the attendance, A. This will be your constraint equation (you know what that is, right?)
Now, the revenue, R, is given by:
R = PA ............the objective equation
you want to maximize R. You must find its derivative and set it to zero and solve for the appropriate quantity of whatever variable you use. of course, you use the constraint equation to solve for one variable in terms of the other and then plug in the expression in the objective equation so that you get the equation in one variable. then proceed to integrate
can you continue?