Fishing boat rental company A costs $7.50 an hour with no initial
fee.  Fishing boat rental company B costs only $5.50 an hour but 
they charge a $25 initial fee.

I need to know how many hours I would have to rent a fishing boat 
so that the charge would be the the same.  [If I knew that number 
of hours, I would then know that if I wanted to rent a fishing boat 
for less than that number of hours, company A would be cheaper, but
if I wanted to rent it for more than that number of hours, company
B would be cheaper.]

Let x = the number of hours when the costs would be the same.

Then the rental cost for company A would be $7.50x and
the rental cost for company B would be $5.50x + $25.

To find the number of hours for which the charge would be the same,
I set those expressions equal:

$7.50x = $5.50x + 25

  7.5x = 5.5x + 25

I subtract 5.5x from both sides:

  2.0x = 25

     x = 25/2

     x = 12.5 hours.

So if I wanted to rent the boat for less than 12.5 hours I would
go with rental company A.  I would choose rental company B only 
if I wanted to rent a fishing boat for more than 12.5 hours. 
   
Edwin