A wooden box has outer measurements $8$ cm, $6$ cm, $4$ cm and inner total surface area $88$ sq cm. The thickness of the wood is —

If the thickness is $t$, the inner edges are $8-2t,\,6-2t,\,4-2t$. Taking $t=1$ gives inner edges $6,4,2$ and inner surface area $2(6\cdot4+4\cdot2+6\cdot2)=88$ sq cm, matching the given value.