4 is really 2 * 2
12 is reallly 2 * 2 * 3
8 is really 2 * 2 * 2
now, the 2 * 2, is repeated in the factoring, so we use it once only. We still have to account for the extra 2 and 3.
therefore, the LCD will be 2 * 2 * 2 * 3, or 24.
after all the slicing in each tray, all pieces will be equal in length in each tray, and there'll be 24 of them in each tray.