First, we simplify the left side of the equation:
\[ 32 + 72 = 104 \]
Next, we simplify the expression on the right side: \[ 4 + 9 = 13 \]
Now we can express the right side as:
\[ \text{blank} \times 13 \]
We want to solve the equation:
\[ 104 = \text{blank} \times 13 \]
To find the value of "blank", we divide both sides by 13:
\[ \text{blank} = \frac{104}{13} \]
Calculating the division:
\[ \frac{104}{13} = 8 \]
Thus, the value that correctly fills in the blank so that the expressions are equivalent is:
\[ \boxed{8} \]