6/50 = 0.12, so the decimal would be 0.12
6/50 = 12%, so the percentage would be 12%
For the last question, I'm not so sure I understand it, but since there are 50kg of fruits already and you want 100 fruits, I would multiply 6/50 by 2.
6/50 * 2 = 12/100, so that would be 12 kg of apples.
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I really hope this helped you!