To find the missing exponent in the denominator, we can set up the equation based on the properties of exponents.
The equation you provided is:
\[ \frac{H^{450}}{H^{?}} = H^{215} \]
Using the property of exponents that states \( \frac{a^m}{a^n} = a^{m-n} \), we can rewrite the left side:
\[ H^{450 - ?} = H^{215} \]
Now, since the bases are the same, we can equate the exponents:
\[ 450 - ? = 215 \]
To find the value of \( ? \), we can solve for it:
\[ ? = 450 - 215 \] \[ ? = 235 \]
Therefore, the missing exponent in the denominator is \( 235 \).