thus Sum (digits (2075,10)) = (Sum <%5,7,0%>) + (Sum <%2%>) by Th1181, AFINSQ_2:55
.= ((Sum <%5,7%>) + (Sum <%0%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((5 + 7) + (Sum <%0%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((5 + 7) + 0) + (Sum <%2%>) by AFINSQ_2:53
.= 12 + 2 by AFINSQ_2:53
.= 14 ; :: thesis: verum