Remember scientific notation (or standard form) is a method employed by Engineers and Scientists, to make large numbers more manageable.

If it makes it easier for you take each term out of standard form

i.e. 0.000072 instead of 7.2 x 10^-5

(when the exponent is negative count the decimal place forward by 5, when exponent is positve move the decimal backawrds)

7.2 x 10^5 = 720,000

🙂

You may need to adjust afterwards to get the decimal point in the right place for standard form (one digit before the decimal point. If you divide the number part by 10, you have to ADD 1 to the exponent.

(7.2)(4.5) x 10^(-5+3) = 32.4 x 10^-2 = 3.24 x 10^-1.

(7.8)(2.8) x 10^(8+11) = 21.84 x 10^19 = 2.184 x 10^20.