Answer:
90 yards per minute
Step-by-step explanation:
Armen's time getting back was 36 -8 = 28 minutes. Then the ratio of times is 28/36 = 7/9.
The ratio of speeds is the inverse of this, so his speed coming back is ...
speed/70 = 9/7
Multiplying by 70 gives ...
speed = 70·9/7 = 90 . . . . yards per minute
