7. (10 points) There is a sufficiently deep water tank with a rectangular base that is 16 cm long and 12 cm wide. Originally, the tank contains 6 cm of water and 6 cm of oil (the oil is above the water). If a block of iron with dimensions 8 cm in length, 8 cm in width, and 12 cm in height is placed in the tank, the height of the oil layer will be $\qquad$ cm.
7. (10 points) There is a sufficiently deep water tank with a rectangular base that is 16 cm long and 12 cm wide. Originally, the tank contains 6 cm of water and 6 cm of oil (the oil is above the water). If a block of iron with dimensions 8 cm long, 8 cm wide, and 12 cm high is placed in the tank, the height of the oil layer is \qquad cm.

【Solution】Solution: According to the analysis, the water height $=16 \times 12 \times 6 \div(16 \times 12-8 \times 8)=9$ (cm). Let the height of the oil layer be $x$ cm, so:

The volume of the oil layer $V=16 \times 12 \times 6=(12-9) \times(16 \times 12-8 \times 8)+(x-3) \times 16 \times 12$, solving for $x$ gives: $x=7$. Therefore, the height of the oil layer is 7 cm.

The answer is: 7