Hannah has 8 over 9 of a pound of birdseed. she put 2 over 3 of a pound of birdseed into her bird feeders. how much birdseed does hannah have remaining?

8/9 - 2/3 = 8/9 - 6/9 = 2/9 of a pound left

She  had 8/9 of a pound of birdseed to begin with.  She used 2/3 of a pound of birdseed into her feeders.  You have to get a common denominator, would be 9 and when you subtract what she used from what she had you get 2/9 of a pound of birdseed left.

A, a concentration gradient must exist