Correct answer is D.
During the first 150 miles, she drove 150 miles at a speed of x miles per hour, so her time was
[tex]150 \text{ miles} = x * t_{1st}[/tex]
where [tex]t_{1st}[/tex] is the time she spent driving the first 150 miles.
On the second half of the trip, she drove at 1.25x miles per hour. There, the equation would be
[tex]150 \text{ miles} = 1.25x * t_{2nd}[/tex]
where [tex]t_{2nd}[/tex] is the time she spent driving the second 150 miles.
Solve both of those equations for the t variables, then add them together. Your answer will be
[tex]t_{1st} + t_{2nd}= \frac{150}{x} + \frac{150}{1.25x}= \frac{150}{x} + \frac{120}{x}= \frac{270}{x} [/tex]
