Answer
$\text{124 feet.}$
Work Step by Step
To find the safe distance $S$ in feet between your car, you must plug in the speed into the equation $S=0.015x^2+x+10$. As the speed is $x=60$, we find the safe distance as follows: $$S=0.015(60)^2+60+10=124$$$$\text{Therefore, the recommended safe distance is 124 feet.}$$
