Question 465504
Let x = number of tickets over 100.
==> price of ticket is 12 - 0.10x
==> number of tickets is 100 + x

==> Income, or revenue, is {{{(100 + x)(12 - 0.10x) = 1200 + 2x - 0.10x^2}}}.  Since the the coefficient of {{{x^2}}} is negative (-0.10), there is an absolute maximum (parabola faces downward).  The x-value that gives the maximum income is {{{-b/(2a) = -2/(2*-0.10) = 2/0.20 = 10}}}. Hence 100 + 10 = 110 tickets must be sold to get maximum income.