I think that since their is no = sign you can’t have just one nimber because you can’t fully simplify... I got 4c-12
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: 
N= 75 (let me know if you need more help)
Answer:
If 5x+12=44 then value of 5x-12 is 20
Step-by-step explanation:
5x + 12 = 44
- The first step, we have to find the value of x
5x + 12 = 44
5x = 44 - 12
5x = 32
x = 32/5
x = 6.4
- After that, insert the value of x into 5x - 12
5x - 12 = ...
5 ( 32/5 ) - 12
= 32 - 12
= 20