7.2. There are broken scales that are off by no more than 500g in their readings. When Alexei weighed the melon, they showed 4kg. When he weighed the watermelon - 3 kg. When he weighed both the melon and the watermelon together - 8.5 kg. What is the actual weight of the melon and the watermelon separately? The scales can err differently each time.
Answer: The melon weighs 4.5 kg, and the watermelon weighs 3.5 kg.

Solution: From the condition, it follows that the melon weighs no more than 4.5 kg. The watermelon weighs no more than 3.5 kg. Therefore, together they weigh no more than 8 kg. On the other hand, from the second condition, it follows that together they weigh no less than 8 kg. Therefore, they weigh exactly 8 kg together. This weight is only achieved with the extreme values of the melon and watermelon weights. Therefore, the melon weighs 4.5 kg, and the watermelon weighs 3.5 kg, as a lower weight would not sum up to 8 kg.

Criteria: Only the answer, answer with verification - 1 point. Correctly written all three weight estimates - 2 points. These points are cumulative.