Play with numbers

1 x 8 + 1 = 9;
12 x 8 + 2 = 98;
123 x 8 + 3 = 987;
1234 x 8 + 4 = 9876;
12345 x 8 + 5 = 98765;
123456 x 8 + 6 = 987654;
1234567 x 8 + 7 = 9876543;
12345678 x 8 + 8 = 98765432;
123456789 x 8 + 9 = 987654321