for n=1, 15+3*43=207, 207/9=23
Assume that this is true for n, and we check it for n+1:
As assumed, the first term, (10n+3*4n+2+5) divides by 9. As for the second term,
9(10n+4n+2), it is a multiple of 9 and 10n+4n+2 is a whole number for any n from Natural numbers. So, both terms divide by 9.