18. Find the hundreds and units digits of the number $72 * 3 *$, if this number is divisible by 45.
18. The desired number is divisible by 45, which means it is divisible by 9 and 5. The unit digit can be 0 or 5. If $72 * 30$, then the hundreds digit is 6, since $7+2+3+0=12$ and 18 is divisible by 9. If $72 * 35$, then $7+2+3+5=17$, so the hundreds digit is 1. Therefore, 72630 or 72135.