
theorem Th1208:
Sum digits(2525,10) = 14
proof
  thus Sum digits(2525,10) = Sum <%5,2,5%>+Sum <%2%> by Th1207,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%5%> + Sum <%2%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%5%> + Sum <%2%> by AFINSQ_2:54
  .= (5 + 2 + 5) + Sum <%2%> by AFINSQ_2:53
  .= 12 + 2 by AFINSQ_2:53
  .= 14;
end;
