7.3 x 10^3 =7300 (since 10 is raised to the third power, the decimal point moves 3 units to the left)
8.2 x 10^2 = 820
7300-820 = 6480
To write the number in scientific notation, move the decimal point to the right, and place it after the first digit.
Then multiply by 10 raised to the number of places that the decimal point moved.
6.5 x 10^3