To find the density of goldfish in the tank, you can use the formula for density, which is:
\[ \text{Density} = \frac{\text{Number of goldfish}}{\text{Volume of the tank}} \]
In this case, the number of goldfish is 12 and the volume of the tank is 45 cubic feet. Plugging in these values:
\[ \text{Density} = \frac{12 \text{ goldfish}}{45 \text{ cubic feet}} = \frac{12}{45} \]
Now, simplifying \(\frac{12}{45}\):
\[ \frac{12}{45} = \frac{4}{15} \approx 0.267 \]
So, the density is approximately 0.27 goldfish per cubic foot.
Thus, the correct answer is:
0.27 goldfish per cubic foot.