Question

What is 7.09x10 to the 5 minus 6.10xto the 4 in scientific notation

Answer 1

When subtracting scientific notation, you first need to make the exponents the same. The standard is to make the smaller exponent the same as the higher one.
Let's take a look at your given:

$7.09 x 10^{5}$
$6.10 x 10^{4}$ This is smaller. 

Every time you add to the exponent, you need to move the decimal. So to make it the same, you need to add 1 to the 4 to get 5. Then move the decimal to the left. Your new notation would be:
$.610 x 10^{5}$

Then you just line up the decimal as you would before subtracting and just copy the base and exponent.
$7.09 x 10^{5}$
- $.61 x 10^{5}$
=
$6.48 x 10^{5}$