1. Find the size of one scoop:

* If 3 scoops = 9 fluid oz, then 1 scoop = 9 oz / 3 scoops = 3 fluid oz

2. Calculate how many scoops are in 128 oz:

* 128 oz / 3 oz/scoop = 42.67 scoops

3. Since you can't have a fraction of a scoop, round down:

* You need 42 scoops to equal 128 oz.