Answers

2016-07-26T14:16:00+08:00
-18 -12.5 -7 -1.5 4

(-18+4)÷2=-14÷2=-7 2nd arithmetic mean
(-7+-18)÷2=-25÷2=-12.5 1st arithmetic mean
(-7+4)÷2=-3÷2=-1.5 3rd arithmetic mean
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