If someone ran a marathon of 26.2 miles in 1 hour, 18 mins. and 27 seconds. how do i find out how many miles per minute they ran

An hour is 60 minutes, plus the 18 minutes = 78 minutes
a minute is 60 seconds, so 78 * 60 = 4680.
Plus the 27 seconds, it's 4707 seconds.
convert it back into minutes, 4707 / 60 = 78.45 minutes
so 26.2 divided 78.45 = 0.33397068196
Round that, so they ran 0.3 miles per minute.