reserve a, b, k, n, m for Nat,
  i for Integer,
  r for Real,
  p for Rational,
  c for Complex,
  x for object,
  f for Function;

theorem Th7:
  p >= 0 implies ex m,n being Nat st n > 0 & p = m/n
proof
  consider m being Integer, k being Nat such that
A1: k > 0 & p = m/k by RAT_1:8;
  assume p >= 0;
  then k>0 & m>=0 or k<0 & m<=0 by A1,XREAL_1:141;
  then reconsider m as Element of NAT by INT_1:3;
  take m,k;
  thus thesis by A1;
end;
