Restaurant D offered the best deal at $13.05 per 9 shrimp because it you but 18 it will only cost you 26.15 but if you buy from restaurant A you only get 16 shrimp for 26.40 so I'd say go wit restaurant D
the price per 1 shrimp is in restaurant A is 13.20/8= $1.65 B is 18.00/20=$ 1.50 C= 10.32/6= $ 1.72 D= 13.05/9= $ 1.45 the answer is that restaurant D offers the best deal per shrimp
