Answer:
192/7 or approximately 27.429 ounces
Step-by-step explanation:
Let the amount of water added, in ounces, be [tex]w[/tex]. Set up the following equation:
[tex]\displaystyle \\\frac{64}{64+w}=0.7[/tex]
Multiply both sides by [tex]64+w[/tex]:
[tex]\displaystyle\\64=0.7(64+w)\\64=44.8+0.7w,\\w=\frac{19.2}{0.7}=\boxed{\frac{192}{7}}[/tex]
