(1+7\33)+(1+7\33×2)+``````+(1+7\33×11)=?

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(1+7\33)+(1+7\33×2)+``````+(1+7\33×11)=?

(1+7\33)+(1+7\33×2)+``````+(1+7\33×11)
=11+7/33×(1+2+……+11)
=11+7/33×(1+11)×11/2
=11+7/33×66
=11+14
=25