Find the greatest 5-digit number divisible by 12.

The greatest 5-digit number is $99999$.Divide $99999$ by $12$ to find the remainder:
$$99999÷12=8333\text{ with a remainder of }3$$
Subtract the remainder from the greatest 5-digit number to get the exactly divisible number:
$$\text{Number}=99999-3=99996$$