1 pound is equal to 16 ounces.
It is given that Neil brought 2 pounds of grapes.
Convert into ounces
2 pounds=32 ounces.
It is also given that 8 ounces of grapes left.
The ounces of grapes that were used are
32-8=24 ounces.
Hence there are 24 ounces of grapes were used.