Volumes of ethanol and water are in the solution : 30 mL and 70 ml
The concentration of a substance can be expressed in several quantities such as moles, percent (%) weight/volume,), molarity, molality, parts per million (ppm) or mole fraction. The concentration shows the amount of solute in a unit of the amount of solvent.
Percent Volume (% v/v) : volume (ml) of solute/100 ml of solution ⇒ ratio of volume of the solute to total volume of the solution
[tex]\tt \%solute=\dfrac{solute~volume}{solution~volume}\times 100\%[/tex].
30% ethanol ⇒30% etanol, 70% water
In 100 mL solution :
[tex]\tt Ethanol=30\%\times 100~mL=30~mL\\\\Water=70\%\times 100~mL=70~ml[/tex]