2 cakes require 10 cups of flour.
16 cupcakes will use 6 cups.
Add up the total to get 16 cups of flour used.
At 4 cups per pound, her 16 used cups of flour weigh 4 lbs. (16/4).
She used 4 lbs from the original 18 lb supply, so when she subtracted that 4 lbs from the 18 lbs she started out with, she discovered she has 14 lbs of flour left to make more goodies!
Hope it correct!!