Answer:
the greatest 5-digit number possible (in base 10) is 99,999.
to find the number you need to get 99,999 from 45,236, subtract 45,236 from 99,999.
99,999 - 45,236 = 54,763.
hence, you need to add 54,763 to 45,236 to get the greatest 5-digit number.