5 m/sec or 300m / min
using speed = 
change 5 min 20 sec to seconds = (5 × 60) + 20 = 320 sec
speed =
= 5m / second or
speed = 60 × 5 = 300m / minute
Your answer would be 15.6
The correct answer is option 2.
3 = 0
x - a = 0
x = a
x + b = 0
x = -b
We do not multiply any of these values by 3 because in a way, 3 is acting as another "zero" of the equation. Though, as shown above, it does not equal 0, it still does not apply to any of the other equations solved above.
Hope this helps!! :)
Out of that particular list, the only description
that applies to 2.5 is "rational".