Question 376748
The basic equation is:

(0.90)(8)+0=(0.70)(8+x)

Solving for x will give you the required amount of water


Alternatively, we can use the method of alligation

0.90-0.70=0.20

0.70-0=0.70

Then the ratio of solution to water=S/W=0.70/0.20

E.g. there are 0.70 parts of solution for every 0.20 parts of water

If there are 8 parts of solution, then 0.70/0.20=8/W

Solving for W, we have 2.2857oz of water (Answer)