Answer
$P(x)=-0.45x+23$
Work Step by Step
The general slope-intercept form of the linear function is:
$P(x)=mx+b$ where m is slope, b is the y-intercept.
Here by the exercise: $m=-0.45$ and $b$ is when $x=0$ i.e. the rate at $1968$, hence $b=23. Thus $P(x)=-0.45x+23$
