What is the sum of 4.2 x 10^5 and 5.3 x 10^5

Definition of Terms.
Coefficients in the above examples 4.2 and 5.3
Base The base of the power is 10
The power is 5
 
Remark
When you are adding, if the powers on the bases are equal (or can be made equal) and the coefficients are between 1 and 10, then you just add the coefficients and put the powers at the end of your answer. The coefficient answer should be between 1 and 10

Solution
Add the coefficients
4.2 + 5.3 =9.6

Add the power of 5 on. There is no need to alter it any way.
9.6 * 10^5. The coefficient is between 1 and 10 so no need to alter that either.