a. 37581 - 9999
= (37581 + 1) - (9999 + 1)
= 37582 - 10000
= 27582
b. 7345 - 1998
= (7345 + 2) - (1998 + 2)
= 7347 - 2000
= 5347
c. 485321 - 99999
= (485321 + 1) - (99999 + 1)
= 485322 - 100000
= 385322
d. 7593 - 1997
= (7593 + 3) - (1997 + 3)
= 7596 - 2000
= 5596