8. Variant 1. A dishonest seller attached a nut to the correct scales, and now the scales overestimate the weight. First, a large apple was placed on the scales, and they showed 300 g. Then a small apple was placed on the scales, and they showed 200 g. When both apples were placed on the scales, they showed 480 g. How many grams does the nut weigh?
Answer: 20.

Solution: The nut's weight affects the total of $300+200=500$ g twice, but only once in the weight of 480 g. Therefore, the weight of the nut is $500-480=20$ g.