thus Sum (digits (2925,10)) = (Sum <%5,2,9%>) + (Sum <%2%>) by Th1231, AFINSQ_2:55
.= ((Sum <%5,2%>) + (Sum <%9%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((5 + 2) + (Sum <%9%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((5 + 2) + 9) + (Sum <%2%>) by AFINSQ_2:53
.= 16 + 2 by AFINSQ_2:53
.= 18 ; :: thesis: verum