Answer: 
Step-by-step explanation:
Let be "x" the original volume of the solution (in milliliters) before the acid was added and "y" the volume of the solution (in milliliters) after the addition of the acid.
Set up a system of equations:

Applying the Substitution Method, you can substitute the second equation into the first equation and then solve for "x":
It would be mark N? I think
Answer:
multiple and divide are depending on the powers ( sometimes the numbers before the scientific n.)
If the power neg- , it's going down
like this 10^-5 = 1/10^5
If the power pos+ , it's the same idea but different in signs .
Adding and subtracting are depending on numbers ( If the scientific n. is the same number) .
for example:
3x10^5 + 4x10^5 = (3+4)x10^5 = 7x10^5