A number that is 500 more than the biggest number that can be formed by all the odd 1 digit numbers."500 more than" signifies that we need to add 500 to whatever number we got."biggest number" tells you to pick the largest number possible under the given conditions (which I will get to right now)."all the odd 1 digit numbers" means using 1, 3, 5, 7, and 9 and arrange them in a way where the number you get is the largest number possible using JUST THOSE numbers. To do this, start off with the largest number, then pick the 2nd largest, then 3rd largest, etc. So the number will be 97,531.
We're asked to add 500 to 97,531, which will give us 98,031, and that's the number that you're looking for.