The answer would be 5.43x10^-7
The first thing you would do is count the zeros preceding the end numbers 543, there are 6 zeros. Now, if you move the decimal place 6 points in the left direction, you will see that you still need one more move so, 7…
You may be wondering, what does this mean?
Well, since we found how we can get to 5.43, we can reverse the process and get to our original number so, 5.43x10^-7
Also, if you were wondering, you cannot increase it. Which means, you can not make it to be, 54.3 or 543… it has to be left than 10…
I apologize for my extensive answer. I couldn’t really think of a short way to put it…
I really hope this helps