I would like to know the difference in inches or feet for a refrigerator that is 20.9 vs 20.7

Assuming that 20x12 means 20 feet by 12 feet, then you take the three values in feet - 20, 12, and .333 (4 inches is 1/3 foot).

Multiply these three numbers to get the cubic feet:
12 x 20 = 240
240 x .333 = 79.92
Now that you have 79.92 cubic feet, to get cubic yards you divide by 9 since there are 9 cubic feet per cubic yard.

79.92 cu. ft. divided by 9 = 8.88 cubic yards (round up to 9).

If those measurements are the inside dimensions it is easy except you need the width L X H X W = AREA but since you are in inches you need feet. so divide that but 1728 it comes out to 36.5

Normally refrigerators have stickers inside that state the cubic feet. If that's missing you must measure the width X depth X height to get cubic feet. WxDxH= cubic feet.

That depends on the length and width.
24 feet 11 inches by 1 inch is about 2.01 square feet.
24 feet by 1 feet is 25 square feet.
20 feet by 5 feet is 100 square feet.
12.5 feet by 12.5 feet is 156.25 square feet.

That depends on how high and how deep the refrigerator is.

For example, if the height and depth are both 27 inches then the volume is about 11.39 cubic feet. If the height is 36 inches and the depth is 27 inches then the volume is about 15.19 cubic feet.

20 inches times 30 inches times 20 inches is 12,000 cubic inches. There are 12 inches in a foot, so one foot is 12^3 or 1728 cubic feet. 12,000 cubic inches divided by 1728 cubic inches per cubic foot is about 6.9 cubic feet.

That would depend on the depth. A refrigerator that's 60 inches high by 30 inches wide by 1 inch deep would be just over one cubic foot. A refrigerator that's 60 inches high by 30 inches wide by 30 inches deep would be 31.25 cubic feet.

The quickest way would be to measure the Volume inside of the unit. Height, Width and Depth. Example: Height 60 inches, width 24 inches, depth 24 inches then divide by 1728(Cubic inches in a Cubic foot 12x12x12). 24x24x60 = 34560 / 1728 = 20 cubic feet

20 cubic feet = 34560 cu inches