Answer
90 g
Work Step by Step
Total mass of the solution= $Density\times Volume= \frac{1g}{mL}\times750 mL=750g$
$Mass\,percent=\frac{Mass\,of\,the\,component\times100}{Total\,mass\,of\,the\, solution}$
That is, 12%=$\frac{Mass\,of\, ethanol\times100}{750\,g}$
$\implies Mass\,of\, ethanol=$$ 12\times\frac{750\,g}{100}= 90\,g$
