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For a given substance, its tells you the mass occupied by one unit of volume of that substance.

In essence, is a measure of how well the molecules of a substance are packed in a unit of volume. In your case, the densities of the two substances are expressed in grams per milliliter, which means that a unit of volume will be $"1 mL"$.

So, mercury has a density of $"13.546 g/mL"$, which means that $"1 mL"$ of mercury will have a mass of $"13.546 g"$. On the other hand, $"1 mL"$ of ethanol will have a mass of $"0.789 g"$.

Your strategy here will be to use the density of mercury to find the mass that occupies $"0.95 L"$, then use the density of ethanol to find the volume that would have an equal mass.

So, you will have - don't forget to convert the volume from liters to milliliters

$ 0.95 color(red)(cancel(color(black)("L"))) * (10^3color(red)(cancel(color(black)("mL"))))/(1color(red)(cancel(color(black)("L")))) * overbrace("13.546 g"/(1color(red)(cancel(color(black)("mL")))))^(color(purple)("density of mercury")) = "12,868.7 g"$

The volume of ethanol that will have an equal mass is

$"12,868.7" color(red)(cancel(color(black)("g"))) * overbrace("1 mL"/(0.789color(red)(cancel(color(black)("g")))))^(color(purple)("density of ethanol")) = "16,310.1 mL"$

Rounded to two and expressed in liters, the answer will be

$"16,310.1"color(red)(cancel(color(black)("mL"))) * "1 L"/(10^3color(red)(cancel(color(black)("mL")))) = color(green)("16 L")$