Question

How do you add `2.2x10^7`, `6.12x10^6`, `1.51x10^7`, and `1.09x10^6`?

Answer 1

You first have to get them to the same `10`power

`6.12*10^6=0.612*10^7`
`1.09*10^6=0.109*10^7`
(decimal point 1 to the left means power goes up by 1)

Now you can add:
`(2.2+0.612+1.51+0.109)*10^7=4.431*10^7`

Dependent of what figures you're adding, you may want to round the result to the appropriate number of significant figures.