To find the y-value of the function \( y = 3(5)^x \) when \( x = -6 \), we can substitute \(-6\) for \(x\) in the function:
\[ y = 3(5)^{-6} \]
Now, calculate \( (5)^{-6} \):
\[ (5)^{-6} = \frac{1}{(5)^6} \]
Next, calculate \( (5)^6 \):
\[ (5)^6 = 5 \times 5 \times 5 \times 5 \times 5 \times 5 = 15625 \]
So, we have:
\[ (5)^{-6} = \frac{1}{15625} \]
Now plug this back into the equation for \(y\):
\[ y = 3 \times \frac{1}{15625} = \frac{3}{15625} \]
Therefore, the y-value when \( x = -6 \) is:
\[ \left(-6, \frac{3}{15625}\right) \]
So, the answer in the format requested is:
\((-6, \frac{3}{15625})\)