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from stat 1, all you know is that either -10 and 7 can be dropped, or -8 and 6 can be dropped. each of these cases leads to a different answer. insuff.
from stat 2, the only possibility of the terms that are dropped is -10 and 7. original range is 7-(-10)=17, and so new range will be 17-3=14, so -8 and 6 must stay. you know the new set, and can find the new average, and thus the percentage change.