I have a clue how to solve this problem, but I need some extra help. Thanks!
4.2 x 10^8 = 4.2 x 108-4 = 2.1 x 104
2 x 10^4 2
I just divided the numbers 4.2 and 2.1 and then I used a law of exponents to subtract the exponents dividing by the same base.
Best of luck,