Answer
$19$ years old; $72$ years old;
Work Step by Step
In order to determine the age group expected to be involved in $10$ fatal crashes per $100$ million miles driven, we solve the equation $f(x)=10$ using the Quadratic Formula:
$$\begin{align*}
0.013x^2-1.19x+28.24&=10\\
0.013x^2-1.19x+28.24-10&=0\\
0.013x^2-1.19x+18.24&=0\\
x&=\dfrac{-(-1.19)\pm\sqrt{(-1.19)^2-4(0.013)(18.24)}}{2(0.013)}\\
&\approx\dfrac{1.19\pm 0.684}{2(0.013)}\\
x_1&\approx 19\\
x_2&\approx 72.
\end{align*}$$
The function does not model the actual data too well because age $19$ corresponds to a number of fatal crashes between $6.2$ and $9.5$ in the bar graph, while the age $72$ corresponds to a number of fatal crashes between $3.8$ and $8$ in the bar graph.
