CATDOLL : CATDOLL: King crabs cost 48 yuan per pound, and scallops cost 35 yuan per pound. If I want to spend 800 yuan on king crabs and scallops, how many pounds of scallops and king crabs do I need?

Since the conditions of the question are limited, we need to use the elimination method to solve it. Assume that the crab is X jin and the shellfish is Y jin, 48X+35Y=800

According to the data, one pound of scallops costs 35 yuan, and the multiples of 35 are 5 or 0. Since the total cost is 800 yuan, the unit digit of the amount spent on king crabs can only be 5 or 0. It is impossible for the multiples of 48 to have a unit digit of 5, so the unit digit of the amount spent on king crabs is 0.

King crab costs 48 yuan per pound, and 800 yuan can only buy 16 pounds. Among 1-16, the only numbers that meet the condition that the unit digit of 48 is 0 are 5, 10 and 15. Substituting the three numbers into 48X+35Y=800 in turn, only 5 meets the condition.

So, I bought 5 kilograms of king crabs and 16 kilograms of scallops.