
theorem Th269:
Sum digits(18,10) = 9
proof
  thus Sum digits(18,10) = Sum <%8%>+Sum <%1%> by Th268,AFINSQ_2:55
  .= 8 + Sum <%1%> by AFINSQ_2:53
  .= 8+1 by AFINSQ_2:53
  .= 9;
end;
