Question 705194
Using x for how many tickets sell, y for price of ticket,
________x___________y
_______10000_______$200
_______11000_______155
_______12000_______110
Slope is -9/200, and plugging any point in to figure y intercept,
{{{y=-(9/200)x+650}}}.  


We can find an expression or formula to determine sales in money using both x and y.  From the linear equation just found, we find {{{x=(650-y)*200/9}}}.
See that sales is x*y, meaning (How many tickets sold)*(ticket price) dollars.


Sales then is {{{y*(650-y)*200/9}}}
The cost to fly one patron is {{{100*y}}}


The profit then is Sales minus Cost, which is:
P(y)={{{y*(650-y)*200/9-100*y}}}
Notice profit here is formed as a function of how many tickets are sold (and assumed matched to the number of ticket holders flown).