A runner's pace is 8 minutes per mile. What is this pace in miles per hour?

The runner covers $1$ mile every $8$ minutes. There are $60$ minutes in an hour, so the runner covers $\frac{60}{8}=7.5$ miles per hour, choice B. Choice D ($12$) divides $60$ by $5$, which would be a $5$-minute mile. Choice C ($8$) reuses the number of minutes as if it were miles per hour. Choice A ($6.5$) subtracts instead of dividing, which does not convert a pace to a speed. Pace and speed are reciprocal measures: a slower pace means a lower speed, and $7.5$ mph is reasonable for an $8$-minute mile.