To solve the equation \( 15^? \div 15^7 = 15^{12} \), we can use the properties of exponents. Specifically, when dividing like bases, we subtract the exponents:
\[ 15^? \div 15^7 = 15^{? - 7} \]
Setting this equal to \( 15^{12} \):
\[ 15^{? - 7} = 15^{12} \]
Since the bases are the same, we can set the exponents equal to each other:
\[ ? - 7 = 12 \]
Now, solve for \( ? \):
\[ ? = 12 + 7 = 19 \]
Thus, the missing number is \( 19 \).
The correct response is:
19