a) 670,000,000 + 700,000,000 = 1,370,000,000
b) Divide 1,370,000,000 by 9 (9 because that is how many digits behind the first comma).
c) You should get 1.37
d) Now, multiply 1.37 by 10^9. You should not actually multiply these numbers; just write your problem.
e) It should look like this: 1.37 x 10^9
