If "0 is not an allowable value for b", then (a/b)*b=a is not defined when b=0, so it is neither true nor false, since you had previously agreed that b=0 is not

If "0 is not an allowable value for b", then (a/b)*b=a is not defined when b=0, so it is neither true nor false, since you had previously agreed that b=0 is not allowed (regardless of what "/" and "*" are meaning in this context).