5.8 x 10^4
So the decimal is at the very end of the number right now, to the right of the 7. What we need to do is try to get the decimal as far to the left as we can while it still being between two numbers that are between 1-10. So we put it in between 5 and 8. The 10^n just means the number of places we moved the decimal to the left. In this case, we moved the decimal 4 times to the left, so it becomes 10^4.