1 yard = 3 feet, so:
12 yards / minute = 12 * 3 feet / minute = 36 feet per minute
To get the result in seconds, we need to divide 36 by 60 (because that's how many seconds are in a minute of course):
36 / 60 = 36 * 1/60 = 6 * 1/10 = 3/5 = 0,6
So:
12 yd/min = 0,6 ft/s