Question 21689
That exponent on a number, like 10, tells
you how many of that number you are going
to multiply.
For example 2^3 means 2*2*2.
So, 10^9/10^7 means you have nine tens in the 
numerator and seven in the denominator.
So, seven of the 10's in the numerator get
canceled leaving you with two or 10^2.
Similarly with the 2's.  You have eight
in the numerator and 3 in the denominator.
You end up with 5 two's in the numerator or 
2^5.

Cheers
Stan H.