Cole has to pay 3 * 9 = $<<3*9=27>>27 for one side of the side fence.
For the shared left fence, he has to pay two-thirds of 27, so he has to pay 27 * 2 / 3 = $<<27*2/3=18>>18.
The shared back fence will cost 3 * 18 = $<<3*18=54>>54.
He has to pay for half the back fence, so it will cost 54 / 2 = $<<54/2=27>>27.
Thus, Cole has to pay 18 + 27 + 27 = $<<18+27+27=72>>72 for the fence.
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