Respuesta :

1/7 gallon  = 1 batch 

[multiply by 7 through]
1 gallon = 7 batches

[multiply by 8/9 through]
8/9 gallon = 7 x 8/9
8/9 gallon = 6 2/9 

[Good enough to make 6 batches, not enough to make 7 batches]

So he can make 6 batches of collard green