To solve the equation \( 4^{-8} \cdot 4^? = 4^{12} \), we can use the properties of exponents.
The property we will use is that \( a^m \cdot a^n = a^{m+n} \). Therefore, we can combine the left side:
\[ 4^{-8} \cdot 4^? = 4^{-8 + ?} \]
Now, we set the two sides equal to each other:
\[ 4^{-8 + ?} = 4^{12} \]
Since the bases are the same, we can set the exponents equal to each other:
\[ -8 + ? = 12 \]
Now, solve for \( ? \):
\[ ? = 12 + 8 = 20 \]
Thus, the missing value is
\[ ? = 20 \]