To find the y-value of the function \( y = 3(5)^x \) when \( x = -6 \), we can substitute \(-6\) for \(x\) in the equation.
\[ y = 3(5)^{-6} \]
Now, we calculate \( (5)^{-6} \):
\[ (5)^{-6} = \frac{1}{(5)^6} \]
Next, we find \((5)^6\):
\[ 5^6 = 15625 \]
So,
\[ (5)^{-6} = \frac{1}{15625} \]
Now we can plug this back into our equation for \(y\):
\[ y = 3 \cdot \frac{1}{15625} = \frac{3}{15625} \]
Therefore, the y-value when \( x = -6 \) is
\[ \frac{3}{15625} \approx 0.000192 \]
So, the y-value is \( \frac{3}{15625} \).