So I would indeed say that x cannot be any number less than, or equal to, 70. In this universe, it probably is not possible to drive exactly 70 miles per hour,

So I would indeed say that x cannot be any number less than, or equal to, 70. In this universe, it probably is not possible to drive exactly 70 miles per hour, because mile or hour may not be an integer multiple of a fundamental unit. Everything would be discretized, including possible speeds. Note that actually only speed differences need to be discrete, as those are the only thing actually observable. You cannot measure any absolute speed in this universe.