How do I explain in words how I get this answer.

0. 0000003415 = 3.4115X10

^{-7} Scientific Notation has always written in the form having only one integer before the decimal point ( 1's digit) and multiplied by powers of 10.

You know that in our decimal numbering system, any number of shift to the left value increases 10 times

In this example, to write it into scientific form we have to shift 7 times to the right, therefore have to

compensated by by multiplying by 10

^{-7}, to maintain the equality. So, scientific notation is, different way of writing numbers.