12 + 17 + 22 +27 + ... + 92 + 97 = 2*(10 + 20 + ... + 90) + 9*(2+7) = 900 + 81 = 981
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12 + 17 + 22 +27 + ... + 92 + 97 = 2*(10 + 20 + ... + 90) + 9*(2+7) = 900 + 81 = 981