So the answer is 14 ounces
Explanation
Since 16.8 is the original plus 20% we could say 16.8=120%
And since X is the original we could say X=100
So using that info we could put it into a proportion
120/100=16.8/x or
120. 16.8
——=. ———-
100. X
Then we cross multiply and divide
So,
120x=16.8(100)
120x=1680 then divide both sides by 120
X=14