Answer
$\displaystyle \lim_{x\rightarrow\infty}S(x)=550.$
Students living in households with extremely high incomes
have an average SAT score that approaches $550$.
Work Step by Step
$x$ is "approaching $+\infty$" means that $x$ is assuming positive values of greater and greater magnitude.
See table below.
As $x$ assumes positive values of greater and greater magnitude,
the function value approaches the value $550$.
So, we write
$\displaystyle \lim_{x\rightarrow\infty}S(x)=550.$
Thus, students living in households with extremely high incomes
have an average SAT score that approaches $550$.
