First, we need to calculate the product of 100 and 18:
\[ 100 \times 18 = 1800 \]
Next, we find the difference between 984 and this product:
\[ 984 - 1800 \]
Calculating this gives:
\[ 984 - 1800 = -816 \]
Therefore, the difference between 984 and the product of 100 and 18 is \(-816\).