
theorem Th976:
Sum digits(759,10) = 21
proof
  thus Sum digits(759,10) = Sum <%9,5%>+Sum <%7%> by Th975,AFINSQ_2:55
  .= (9 + 5) + Sum <%7%> by AFINSQ_2:54
  .= 14 + 7 by AFINSQ_2:53
  .= 21;
end;
