To find the missing number in the expression \( 7^? \div 7^5 = 7^{12} \), we can use the quotient rule of exponents, which states that:
\[ \frac{a^m}{a^n} = a^{m-n} \]
Applying this to the given equation:
\[ 7^? \div 7^5 = 7^{? - 5} \]
Setting that equal to \( 7^{12} \), we have:
\[ 7^{? - 5} = 7^{12} \]
Since the bases are the same, we can set the exponents equal to each other:
\[ ? - 5 = 12 \]
Now, solve for \( ? \):
\[ ? = 12 + 5 = 17 \]
Thus, the missing number is \( 17 \).