To determine the number of foxes after 30 years using the model given by the function \( y = 40 \times 3^x \), we first need to calculate how many 10-year periods are in 30 years.
Since 30 years corresponds to \( 30 \div 10 = 3 \) periods of 10 years, we can substitute \( x = 3 \) into the function:
\[ y = 40 \times 3^3 \]
Now we calculate \( 3^3 \):
\[ 3^3 = 27 \]
Next, we multiply this by 40:
\[ y = 40 \times 27 = 1080 \]
Thus, after 30 years, there will be 1080 foxes.