Question 1011434
use  the linear function 
{{{T = 10x + 1000}}}

If they increase the ticket price to ${{{15}}},the linear function will be:

{{{T = 15x + 1000}}} 

to find out how many tickets will they have to sell to have a total of ${{{4000}}} in the account,substitute {{{T}}} with {{{4000}}} and solve for {{{x}}}

{{{4000 = 15x + 1000}}}

{{{4000-1000 = 15x}}} 

{{{3000 = 15x }}}

{{{x=3000/15}}}

{{{x=200}}}

They will have to sell {{{200}}} tickets and answer is C.