[tex]\bf p+\cfrac{x}{2}=33\qquad
\begin{cases}
p=percentage\\
x=\textit{years since 1970}\\
----------\\
x=2010-1970\\
\qquad 40\\
p=16
\end{cases}\implies 16+\cfrac{40}{2}=33
\\\\\\
16+20=33\impliedby \textit{are they really equal?}[/tex]
if they're not equal, then the model is off
if the number on the left is higher, the model is underestimating it, if it's lower, is overestimating it, is giving a higher value when is really a low one
