To find the missing exponent in the equation
\[ 7^? \times (7^5)^4 = 7^{34} \]
we start by simplifying the left side of the equation. Using the property of exponents \((a^m)^n = a^{m \cdot n}\), we can rewrite \((7^5)^4\) as:
\[ (7^5)^4 = 7^{5 \cdot 4} = 7^{20} \]
Now substituting this back into the equation gives us:
\[ 7^? \times 7^{20} = 7^{34} \]
Using the property of exponents \(a^m \times a^n = a^{m+n}\), we can combine the terms on the left side:
\[ 7^{? + 20} = 7^{34} \]
Since the bases are the same, we can set the exponents equal to each other:
\[ ? + 20 = 34 \]
To find the missing exponent \(?\), we subtract 20 from both sides:
\[ ? = 34 - 20 = 14 \]
Thus, the missing exponent is:
\[ \boxed{14} \]