When we want to add or substract two numbers that are multiplied by a power of 10, the power of 10 must be the same on both numbers.
In this case we have:
[tex]7\times10^5-5.8\times10^5[/tex]Since
7 - 5.8 = 1.2
Then:
[tex]7\times10^5-5.8\times10^5=1.2\times10^5[/tex]Since the first number of the result is from 0 and 10, then it is already scientifc notation
