Tableau sorts using the leftmost dimension. So you can put a discrete copy of SUM(Growth %) on the Rows shelf at the left, followed by a discrete copy of minus the SUM(Last 3 Month Avg Units). (minus to get the descendant order). This will give you the sorting you are looking for.
Next you can right-click those two blue pills and uncheck 'Show Header' to hide the sorting values.
note: I had to Round the Growth % ROUND( [Growth %] , 2) because even if you display a % with 0 decimals, behind the hood the two 96% are actually two different numbers, as you can see on sheet 3. And they must be the same value if you want the corresponding Last 3 Month values to be sorted.
shorting(mc).twbx 48.8 KB