You have the correct expression for the first answer box. It is s^3+12. Nice work.
The reasoning is that s^3 is the volume of the storage container on the left, and 12 is the volume of the storage container on the right. Adding the two container volumes gets the total volume.
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For the second answer box, we'll plug in s = 4 to get
s^3 + 12 = 4^3 + 12 = 64 + 12 = 76
The total volume is 76 cubic feet.
So 76 is the answer to the second box