42 raspberries, blackberries, and blueberries were picked in total. If half of all the berries had been raspberries, and a third of the berries were blackberries, how many of them were blueberries? Let's be accurate as possible.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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42 / 2 = 21 raspberries had been picked. 42 / 3 = 14 blackberries had been picked. 21 + 14 = 35 raspberries and blackberries had been picked. 42 - 35 = 7 blueberries had been picked.
The answer: 7.