Will mark is it possible to remove ten unit cubes from a 3 by 3 by 3 cube made from 27 unit cubes so that the surface area of the remaining solid is the same as the surface area of the original 3 by 3 by 3 cube? in how many different ways can this be done?

I removed the 3 cubes from the centre of the big cube (the central column) obtaining an increase of the surface area with 10 units.

I removed a column (3 cubes) from one (any) corner of the big cube obtaining an increase with altogether 8 units of the surface area.

I removed another column, placed in the middle of a side, adjacent to the removed corner, obtaining the same surface area as at the beginning.

I removed a corner cube, not adjacent to those removed.

As example is sketched below: See picture attached.

8(-10x+3.5y-7)

8×-10x + 8×3.5y + 8×-7

-80x + 28y - 56

therefore

-80x+28y-56 is the correct answer