Answer:
2
Step-by-step explanation:
( 3 - 4 ) ( - 2 )
= ( - 1 ) ( - 2 )
= 2
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: 
See attachment for the answer: