
theorem Th147:
Sum digits(98,10) = 17
proof
  thus Sum digits(98,10) = Sum <%8%>+Sum <%9%> by Th146,AFINSQ_2:55
  .= 8 + Sum <%9%> by AFINSQ_2:53
  .= 8+9 by AFINSQ_2:53
  .= 17;
end;
