Answer
$y=0.135p+0.15$
Jobs created at $ 50\%$ recovery level: about $7.$
Work Step by Step
The regression line is
$\qquad y=mx+b$,
where $m$ and $b$ are computed as follows.
$m=\displaystyle \frac{n(\sum xy)-(\sum x)(\sum y)}{n(\sum x^{2})-(\sum x)^{2}}\qquad b=\frac{\sum y-m(\sum x)}{n},$
$n=$ number of data points.
$\left[\begin{array}{lllll}
& p & y & py & p^{2}\\
& & & & \\
\hline & 20 & 3 & 60 & 400\\
& 40 & 6 & 240 & 1600\\
& 80 & 9 & 720 & 6400\\
& 100 & 15 & 1500 & 10,000\\
\hline & & & & \\
\sum & 240 & 33 & 2520 & 18,400\\
& & & &
\end{array}\right]$
$m=\displaystyle \frac{4(2520)-(240)(33)}{4(18,400)-(240)^{2}}=\frac{27}{200}=0.135$
$b=\displaystyle \frac{33-(0.135)(240)}{4}=0.15$
$y=0.135p+0.15$
When $p=50$ (percent),
$y=0.135(50)+0.15=6.9\approx 7\quad $ (jobs created)
