Can someone me this question and explain/show your work to get that answer? ?

If the number increases each year, then the 15% starts with a bigger number each year.

The first increase raises 300 million to (1.15 times 300 million) = 345 million.

The next increase raises 345 million to (1.15 times 345 million) = 396.75 million.

and so on and so on. 

This is just like compound interest in a bank.  Each time the bank
pays you interest on your savings, it pays interest on a bigger amount.

In this problem, the number of cars increases

   ... at the end of 2000 / beginning of 2001  
   ... at the end of 2001 / beginning of 2002  
   ... at the end of 2002 / beginning of 2003
   ... at the end of 2003 / beginning of 2004  .

That's four times.  Each increase raises it 15% higher than it was before.
So you need to find

        (1.15) · (1.15) · (1.15) · (1.15) of 300 million.

The way to write that is

         (300 million) · (1.15)⁴   =      524 million 701 thousand 875 cars.

Rounded to the nearest whole million, that's  525 million.