Centimeter , millimeter ,decameter ,meter and kilometers all are the units of measurement. They used to measure the distance. Among all these units of measurement, kilometer is largest unit to measure distance and and millimeter is the smallest unit. After millimeter , we will consider centimeter ,than meter and decameter. So the correct order is Millimeter< centimeter <meter< decameter<kilometer
Ranger is incorrect. The expression, 8x – 20, is in its simplest form because there are no parentheses and no like terms. The two terms cannot be combined because only one term has x as its variable.