To find \(-99.85 - 16.98\) using the additive inverse, we can rewrite the expression as follows:
The additive inverse of \(16.98\) is \(-16.98\). So, we can reframe the subtraction:
\[ -99.85 - 16.98 = -99.85 + (-16.98) \]
Now, we can add the two negative numbers together:
\[ -99.85 + (-16.98) = - (99.85 + 16.98) \]
Now let's calculate \(99.85 + 16.98\):
\[ 99.85 + 16.98 = 116.83 \]
Thus, we have:
\[
- (99.85 + 16.98) = -116.83 \]
So, the result of \(-99.85 - 16.98\) is:
\[ \boxed{-116.83} \]