The first set of numbers are in standard form while the other is in scientific notation.
Scientific Notation is a process in which makes a long numbered number into a shorter version.
To make a number scientific notation, you must put the first number between 0-10.
The problem would be 6.7 x 10^-4 - 2.3 x 10^5. The answer would be 4.4 x 10^1. First you have to know what to do with the powers. You subtract them because it is a subtraction problem. Then you subtract the numbers and then you have the answer.