Jake wants to post a 600 gram parcel and an 800 gram parcel.
He posts them Second Class.
He pays with a £10 note.
How much change should he get?
1. The combined volume of all the tanks at the aquarium is written in Scientific notation. Keeping this on mind, you can write it as following:

2. Now, you must sum the combined volume of all the tanks and the volume of the new tank to calculate the total volume of all of them:
3. Now, you can write the result in Scientific notation, as following:

The answer is: 
9-2(-3)+6= 9+6+6 Your answer should be 21 if I read your question correctly
Answer:
I think the answer is option A