
theorem Th68:
Sum digits(77,10) = 14
proof
  thus Sum digits(77,10) = Sum <%7%>+Sum <%7%> by Th67,AFINSQ_2:55
  .= 7 + Sum <%7%> by AFINSQ_2:53
  .= 7+7 by AFINSQ_2:53
  .= 14;
end;
