thus Sum (digits (2275,10)) = (Sum <%5,7,2%>) + (Sum <%2%>) by Th1193, AFINSQ_2:55
.= ((Sum <%5,7%>) + (Sum <%2%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((5 + 7) + (Sum <%2%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((5 + 7) + 2) + (Sum <%2%>) by AFINSQ_2:53
.= 14 + 2 by AFINSQ_2:53
.= 16 ; :: thesis: verum