thus Sum (digits (950,10)) = (Sum <%0,5%>) + (Sum <%9%>) by Th1117, AFINSQ_2:55
.= (0 + 5) + (Sum <%9%>) by AFINSQ_2:54
.= 5 + 9 by AFINSQ_2:53
.= 14 ; :: thesis: verum