Question 965722
b, how many Bikes bought.
The owner's purchase price was {{{1000/b}}} dollars per bike.


Owner sold {{{b-10}}} bikes at {{{1000/b+40}}} dollars per bike.


Profit is revenue minus cost.
{{{300=(1000/b+40)(b-10)-1000}}};
Understanding all that discussion is most important.  Solving the equation should be uncomplicated.