Answer:
multiply by feet per mile and divide by seconds per hour
Step-by-step explanation:
To get the desired units, multiply by a factor that is equal to 1, but has the desired units in the numerator and the units you're converting from in the denominator.
For units in the denominator that you want to change, use the inverse of the above multiplier.
We have miles/hour, which has miles in the numerator. We want feet/second, which has feet in the numerator, so we need to multiply by the ratio of feet per mile: 5280 ft/mi.
We also have hours in the denominator, where we want seconds. So, we divide by the factor 3600 s/h.