Question 290255
You forgot the x^2 in the first term which caused this equation to be a straight line rather than a parabola.
 
t= -0.2x^2 + 12x + 11 
opens down - Notice the x^2 term is minus
This is a parabola like the St Louis Arch .
It rises then peaks and falls
The graph below doesn't show the arch because the numbers shown are too small
*[invoke quadratic "x", -.2, 12,11 ]
The solutions tells when t is zero.
The peak will be -b/2a=-12/-2*.2=120/4=30
-b/2a is the x of the vertex and the axis of symmetry.
 The peak occurs on the 30th day.
The last day is 60.9 or on the 61st day
And apparently some tickets were sold the day before tickets were sold.