Answer:
7.2 x 10^8
Explanation:
First I would suggest just to help the people who answer the questions to use (^) when saying its to the power of something
So all you have to do is do (7.8 x 10^8) - (1.5 x 10^9) put that in your claculator and you will have the answer, so it might come out as negative don't worry just ignore the negative sign in this case at least and then it will come out as 720,000,000 so all you have to do is first make this number less than ten so it would be 7.2 then you have to count all the decimal places so you would count the .20000000 which there are 8 decimal places
so your answer is 7.2 x 10^8
:)