Personally, I did this in a kinda weird way but I think that it should be correct
-How I figured the answer out-
I took 11g and wrote 80% next to it, because after all it has 80% less fat than the regular cookie.
Then, I scaled it down to 10% by dividing by 8, which got me
1.375g = 10%
And finally, I multiplied by 10 to now have 100% (meaning, a regular serving size cookie) and be left with the result: 13.75g
-The answer-
13.75g (don't forget to write the units)
Have a great day :)