The given rate is m/h, but that's in terms of meters per hour. The question asks for meters per x minutes, so we should start by converting the rate to meters per minute.

To do so, multiply the rate by one, but in a particular way. Since 1 hour = 60 minutes, (1 hour / 60 minutes) equals one:

(m meters / h hours) x (1 hour / 60 minutes) = (m meters / 60h minutes)

We're looking for the number of meters that corresponds with x minutes. Call that number of meters y, which is our object. The math from here is essentially a ratio, in which we set the given rate equal to the ratio of the number of meters we're looking for to x minutes:

(m meters / 60h minutes) = (y meters / x minutes)
m/60h = y/x
y = mx/60h, choice (E).