IF I PURCHASE AN ITEM FOR $2.00 AND I WANT TO RESELL IT WITH A MARGIN OF GROSS PROFIT OF 64.5% WHAT FORMULA DO I USE TO ARRIVE AT THAT RESELL FIGURE?

Percent means "per one-hundred" so 64.5% is  ^64.5/₁₀₀. Thus if you want your gross profit to be 64.5% you need to add 64.5% of $2.00.

64.5% of $2.00 is

Thus your resell amount should be $2.00 + $1.29 = $3.29

To accomplish this in one step you can calculate