Hello! Here's one way to do it.
Say, you take the 322.50 example you provided. Since .25% was deducted, this means that 322.50 is 75% of the original total, or 3/4. Now, you can set an equation. 322.50 = 3/4x.
To get x (in this case, it means 100%), you can do a few things. One option is to divide by 3, then multiply by 4. Another option is to multiply by 4/3 (or just the reciprocal in general). All of these things work, but the multiply by the reciprocal is what is the easiest, personally.
Let's use the example you gave:
322.50 = 3/4x
322.50 * 4/3 = x
x = 430
Hope this helps!
